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Dissertations |
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1
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VITOR ALENCAR NUNES
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COMPATIBILITY AND ADHESION BETWEEN FIBER-REINFORCED ALKALI-ACTIVATED REPAIR MORTAR AND CONCRETE SUBSTRATE
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Advisor : PAULO HENRIQUE RIBEIRO BORGES
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COMMITTEE MEMBERS :
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PAULO HENRIQUE RIBEIRO BORGES
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PETER LUDVIG
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CRISTINA ZANOTTI
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RUBY MEJÍA DE GUITIERREZ
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Data: Jan 15, 2018
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Concrete repairing is a complex task that requires a special knowledge of technical building regulations and standards, deterioration mechanism and diagnosis, repair principles and methods, repair materials, execution of repair works, inspections, monitoring and maintenance. So far, most used patch repair mortars fall into two categories, (i) the mortars based on inorganic binders (Portland cement, PC) and (ii) those based on organic binders (polymers). Recent investigations reveal a third category of mortars with high potential to be used in the field of concrete repair, i.e. the alkali-activated based mortars. Alkali-activated materials (AAM) have been widely promoted as a greener binder for sustainable constructions. These binders can be generated from a wide range of aluminosilicate materials under alkaline conditions to produce a hardened component. This study, therefore, aims to evaluate the compatibility and the adhesion between a fiber-reinforced alkali-activated mortar and a concrete substrate. Different formulations of AAM were initially studied, based on the alkaline activation of metakaolin (MK) and blast furnace slag (BFS); their mechanical properties and modulus of elasticity were assessed. Five formulations were selected after this preliminary evaluation in order to produce the repair mortar and to apply onto concrete substrates. A volume fraction of 0.25% of PP fiber was used to mitigate the early-age shrinkage and to increase the adhesion bond of the repair mortar with the concrete substrate. The bond strength was evaluated by pull-off testing. The crack and delamination behaviour were assessed by four-point bending tests. Physical properties were also investigated: water absorption, apparent porosity and apparent density. Results showed a good compatibility and adhesion between alkali-activated repair mortars and the PC substrate. Satisfactory bond strengths were found meeting the required by the structure repair standard BS EN 1504. The delamination issue was observed only in 100 % MK-based mortars and the crack propagation behaviour was typical from brittle materials and can be improved with the fiber reinforcement. The formulation 80MK-20BFS designed with SiO2/Al2O3 molar ratio 3.0 and fiber-reinforced was selected as the most promising one to structural repair proposes.
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2
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VANESSA VILELA ROCHA
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DIFERENTES ESTRATÉGIAS DE DISPERSÃO DE NANOTUBOS DE CARBONO PARA PREPARAÇÃO E CARACTERIZAÇÃO DE NANOCOMPÓSITOS DE CIMENTO
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Advisor : PETER LUDVIG
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COMMITTEE MEMBERS :
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CONRADO DE SOUZA RODRIGUES
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JOSÉ MÁRCIO FONSECA CALIXTO
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PETER LUDVIG
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Data: Jan 25, 2018
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Os nanotubos de carbono (NTCs) têm sido estudados devido às extraordinárias propriedades apresentadas, como elevada resistência a tração e baixa densidade. Dessa forma, eles são considerados excelentes materiais para preparação de compósitos objetivando o aprimoramento das propriedades dos materiais à base de cimento. Porém, a dispersão efetiva dos NTCs é crucial para alcançar melhorias nas propriedades mecânicas, e o principal desafio para a incorporação de NTCs na matriz de cimento Portland é a natureza hidrofóbica, fazendo com que em meio aquoso eles tendam a aglomerar.
O presente trabalho, visando o estudo de argamassas e pastas de cimento nanoestruturados com NTCs, analisou diferentes técnicas de dispersão. Foi verificado a dispersão dos NTCs em surfactantes à base de lignosulfonato e policarboxilato em meio aquoso por meio do granulômetro a laser, sugerindo a dispersão efetiva do nanomaterial em presença dos aditivos em solução aquosa. No entanto, ensaios de caracterização mecânica das pastas de cimento com NTCs em proporções de 0% à 0,50% dispersos nos mesmos aditivos com uso de frequências ultrassônicas não indicaram ganhos de resistência expressivos, sugerindo que nas proporções estudadas a dispersão dos NTCs não ocorreu de maneira efetiva.
Dispersando os NTCs nas partículas de cimento em meio não aquoso de isopropanol e sonificação em proporções de 0%, 0,05% e 0,10%, no entanto, foi alcançado ganhos de resistência à compressão e tração por compressão diametral de aproximadamente 50% para o incremento de 0,05%, sugerindo forte ligação entre o nanomaterial e as partículas de cimento. O ganho de resistência a flexão alcançou 12% também para as pastas de cimento com 0,05%, sugerindo que o limite de dispersão por tal metodologia foi alcançado nessa proporção.
Além disso, as pastas de cimento com 0,05% de NTCs apresentaram aumento de 70% na energia de fratura e 14% na tenacidade a fratura, sugerindo que em tais proporções os NTCs estão bem ligados aos produtos de hidratação e atuam como controladores da propagação da fissura.
A mesma técnica de dispersão em meio a solução de isopropanol foi adotada para verificar a dispersão dos NTCs nas partículas de areia fina e média fina e preparação de argamassas. Os resultados, no entanto, não identificaram ganhos de resistência tão expressivos quanto observado para a preparação das pastas de cimento, o que sugere forte interação entre o nanomaterial e as partículas de cimento e fraca interação entre os NTCs e as partículas de areia.
Ensaios de caracterização física foram consistentes aos resultados de caracterização mecânica e identificaram refinamento de poros nas pastas de cimento com NTCs dispersos em isopropanol. Os ensaios de termogravimetria além de sugerir redução de porosidade, sugerem também maior presença de silicato de cálcio hidratado (C-S-H) em presença dos NTCs. Em imagens microscópicas foi possível visualizar filamentos de NTCs disperso nas partículas de cimento anidro após processo de dispersão em isopropanol e sonificação, e as imagens obtidas dos NTCs após 30 minutos de sonificação em presença de isopropanol e evaporação sugerem que não houve danos na estrutura do nanomaterial por meio de tal processo.
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3
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PEDRO VALLE SALLES
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Avaliação mecânica e de durabilidade de concretos fabricados com resíduos de construção e demolição.
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Advisor : CONRADO DE SOUZA RODRIGUES
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COMMITTEE MEMBERS :
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CONRADO DE SOUZA RODRIGUES
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FLAVIA SPITALE JACQUES POGGIALI
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PETER LUDVIG
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WHITE JOSE DOS SANTOS
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Data: Jan 25, 2018
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The use of recycled aggregates in Brazil is limited, being restricted to non-structural functions. The large heterogeneity of the construction and demolition waste (CDW) makes it difficult to systematically use these residues in structural concrete, despite the fact that this application already occurs in several countries, supported by technical standards. Thus, the present dissertation proposes to analyze the effects of replacements (25, 50 and 100%) of natural aggregates (NA) with recycled aggregates of construction and demolition (three different types) in structural concrete. The mechanical haracteristics and durability of these new concretes are measured. In view of the heterogeneity of the CDW composition, a methodology for separation and cleaning of the cycled aggregates is presented. The natural aggregates and the three types of residues were characterized and the lower quality - for the production of structural concretes - of the CDW in relation to the NA was confirmed, being the recycled aggregate of higher quality the CRA followed by the MRA and RRA. The CDW present smaller masses, higher water absorption, higher void volumes and lower abrasion resistance, in relation to natural aggregates. With the recycled concrete specimens ready, the following tests were carried out: Slump; Compressive strength; Static modulus of elasticity; Tensile strength by diametrical compression; Water absorption by immersion; Electrical resistivity test of concrete; Accelerated carbonation test. In general, the use of CDW affects the characteristics of the concrete. Workability, compressive strength, void index, water absorption and modulus of elasticity are parameters negatively affected by the addition of CDW. The resistance to the advance of the carbonation front is an improved feature with the use of recycled aggregates. Regarding the existence of diametrical compression traction, the use of RCD did not affect this parameter.
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4
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RAQUEL PEREIRA BATISTA
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INTERFERÊNCIA DA COMPOSIÇÃO DA MATRIZ NO DESEMPENHO MECÂNICO DE COMPÓSITOS ÁLCALI-ATIVADOS REFORÇADOS COM FIBRAS CURTAS DE PVA
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Advisor : PAULO HENRIQUE RIBEIRO BORGES
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COMMITTEE MEMBERS :
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FERNANDO SOARES LAMEIRAS
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FLAVIA SPITALE JACQUES POGGIALI
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FLAVIO DE ANDRADE SILVA
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PAULO HENRIQUE RIBEIRO BORGES
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Data: Feb 1, 2018
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Alkali-activated materials (AAM), similarly to Portland cement based mortars and concrete, are brittle materials that may have their mechanical behavior improved using fibers. They are currently the subject of increasing interest and research as they present superior performance in many aspects when compared to traditional products. Several types of fibers have already been employed in the production of alkali-activated composites. Poly vinyl alcohol (PVA) seems to be a good choice due to its excellent interaction with the matrix and high stability in alkaline environments. This research investigates the effects of the amount of soluble silica present in the activator on the mechanical and durability-related performance of PVA-reinforced alkali-activated mortars. The composites studied were obtained from the alkaline activation of metakaolin (MK) and in each formulation this precursor material was partially replaced by silica fume (SF), with the purpose of adjusting the SiO2/Al2O3 molar ratio of the matrix. The activator solution used consists of sodium silicate (Na2SiO3), sodium hydroxide (NaOH) and the dissolved SF. Two SiO2/Al2O3 molar ratios were employed: 3.0 and 3.8. The other activating parameter, i.e. Na2O/SiO2, Na2O/Al2O3 and H2O/Na2O molar ratios were held constant, as well as the amount of aggregates used in each formulation. All formulations were reinforced with 2% vol. of PVA fibers. The mechanical properties investigated were compressive and flexural strength. The Young's Module of the mortars was also determined. Apparent porosity tests were used to give an estimation of the durability of the AAM. Preliminary results indicate that the mechanical performance of PVA-reinforced AAM is influenced by the SiO2/Al2O3 molar ratio of the matrix. In addition, the toughness of the composites may be influenced mainly by the source of soluble silica in the activator and by the apparent porosity of the matrices.
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5
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Marcela Palhares Miranda
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AVALIAÇÃO EXPERIMENTAL DA INFLUÊNCIA DAS CARACTERÍSTICAS DO CORPO DE PROVA NO ENSAIO DE ARRANCAMENTO (PULL-OUT TEST)
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Advisor : ELIENE PIRES CARVALHO
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COMMITTEE MEMBERS :
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CLAUDIO JOSE MARTINS
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ELIENE PIRES CARVALHO
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JOSÉ MÁRCIO FONSECA CALIXTO
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NILTON DA SILVA MAIA
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Data: Feb 6, 2018
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A aderência entre aço-concreto é a propriedade que garante viabilidade das estruturas de concreto armado, impedindo que as barras de aço deslizem no interior do concreto. A avaliação da aderência é realizada por meio de ensaios mecânicos, sendo o Ensaio de arrancamento o mais utilizado em estudos sobre a aderência. A geometria do corpo de prova (CP) do ensaio de arrancamento é um parâmetro em destaque na literatura, já que estudos indicam melhorias na distribuição de tensões no interior do corpo de prova com geometria cilíndrica. No que diz respeito ao diâmetro das barras, poucos estudos avaliam o fenômeno considerando apenas as barras finas de aço, que apresentam destaque na construção civil. Dessa forma, este trabalho avaliou a aderência entre barras finas de aço CA-50 (6.3, 8 e 10 mm) e concreto C30. Foi adotado o ensaio de arrancamento, utilizando corpos de prova cúbicos e cilíndricos com comprimentos de ancoragem das barras iguais a 10ϕ.
As tensões de aderência obtidas foram superiores para a geometria cilíndrica, apresentaram baixa variabilidade. Além disso, o teste estatístico comprovou a influência da geometria do molde sobre os resultados do ensaio de arrancamento. Porém, as barras de aço com diâmetro de 6,3 mm apresentaram comportamento distinto aos demais diâmetros. O cálculo do parâmetro do coeficiente de conformação superficial, a partir de dados de ensaio, apontou um ganho de desempenho de aderência para as barras estudadas, já que o valor obtido foi superior ao prescrito pela norma ABNT NBR 7480 (2007).
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6
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SÂMARA FRANÇA
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Blocos álcali ativados de resíduos industriais compactados
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Advisor : MARIA CRISTINA RAMOS DE CARVALHO
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COMMITTEE MEMBERS :
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AUGUSTO CESAR DA SILVA BEZERRA
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FLAVIA SPITALE JACQUES POGGIALI
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MARIA CRISTINA RAMOS DE CARVALHO
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SOFIA ARAÚJO LIMA BESSA
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Data: Feb 6, 2018
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Dentre as técnicas construtivas existentes, o uso do bloco de terra compactado se destaca por se tratar de um produto que dispensa a fase de queima, além dos benefícios como desempenho térmico e acústico em acordo com as normas vigentes. Entre os modos de estabilização do bloco está a estabilização química que pode ser realizada por meio da ativação alcalina. A ativação alcalina consiste na obtenção de um aglomerante a partir de materiais aluminossilicatos em soluções altamente alcalinas. Os blocos compactados possuem a capacidade de incorporar resíduos industriais. Diante disso, dois resíduos gerados em grande volume por processos industriais, cinzas produzidas por termoelétricas a partir da biomassa de eucalipto e o rejeito de minério de ferro, foram utilizados para confecção de blocos compactados ativados alcalinamente. Como contribuição para o desenvolvimento sustentável, o objetivo deste trabalho foi desenvolver blocos utilizando estes resíduos respeitando-se as exigências normativas. A cinza e o rejeito foram caracterizados por microscopia eletrônica de varredura, espectrometria de fluorescência de raios X, difração de raios X, análise térmica diferencial e termogravimétrica, perda ao fogo, granulometria por difração a laser. Foram propostas três relações de composição no ativador (SiO2/Na2O = 1,00, 1,55 e 1,85) e três proporções de cinza e rejeito diferentes (30-70, 50-50 e 70-30). Estes traços foram caracterizados por resistência à compressão e absorção de água aos 7 e 28 dias. O traço com a relação cinza/rejeito 70/30 e SiO2/Na2O 1,55 apresentou o melhor desempenho e por isso foi selecionado para confecção dos blocos. Os blocos foram submetidos a ensaios de resistência à compressão, absorção de água, lixiviação e expansibilidade. Os blocos apresentaram resultados satisfatórios em todos os testes realizados.
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7
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Mariana Rezende Schuab
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ESTUDO DAS VARIAÇÕES DIMENSIONAIS DE ARGAMASSAS ÁLCALI-ATIVADAS E SUA COMPATIBILIDADE COM SUBSTRATO DE CONCRETO DE CIMENTO PORTLAND VISANDO A SUA APLICAÇÃO COMO MATERIAL DE REPARO ESTRUTURAL
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Advisor : PAULO HENRIQUE RIBEIRO BORGES
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COMMITTEE MEMBERS :
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PAULO HENRIQUE RIBEIRO BORGES
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CONRADO DE SOUZA RODRIGUES
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WHITE JOSE DOS SANTOS
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TÚLIO HALLAK PANZERA
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Data: Feb 8, 2018
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As patologias existentes em estruturas envelhecidas de concreto armado requerem a execução de intervenções, que variam desde um reparo superficial a um reforço mais complexo. As argamassas álcali-ativadas têm sido recentemente estudadas na execução de reparos estruturais como materiais alternativos aos constituídos por cimento Portland e por resinas poliméricas. Tal utilização justifica-se pelo fato de as argamassas álcali-ativadas apresentarem desempenho satisfatório, podendo ser superior ao dos materiais convencionais. Há ainda uma motivação adicional ao desenvolvimento desses materiais, que alia o desempenho satisfatório ao interesse no desenvolvimento de aglomerantes com baixa emissão de CO2 e de consumo energético. Este trabalho avaliou o desempenho de 21 diferentes formulações preliminares de argamassas ativadas alcalinamente, compostas por metacaulinita e escória de alto forno. A trabalhabilidade das argamassas foi fixada para todas as formulações, por ser considerada uma característica fundamental para a aplicabilidade e para a utilização proposta. Após a avaliação do comportamento mecânico das formulações preliminares, através do qual foi considerada a compatibilização entre as argamassas e o substrato composto por concreto de cimento Portland, foram selecionadas 5 formulações. Para as quais foi avaliado o efeito da adição de 0,25% de fibras de polipropileno com 6 mm de comprimento. As formulações selecionadas, com e sem a adição de fibras, foram aplicadas sobre substratos de concreto. Os painéis constituídos por concreto e argamassa foram então avaliados por meio de registros digitais de imagens, os quais foram utilizados na mensuração da ocorrência de fissuras provenientes da retração com restrição. Tais painéis foram também, posteriormente, submetidos à avaliação da aderência. Observou-se que a adição de 0,25% de fibras não foi eficiente no combate à retração nas primeiras idades. Além disso, constatou-se que a substituição de 20% de metacaulim por escória contribuiu para a redução do número de fissuras e também do comprimento de fissuras. Contudo, as argamassas com os maiores teores de escória avaliados não apresentaram desempenho satisfatório para as variáveis analisadas.
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8
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ANIEL DE MELO DIAS
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MANIFESTAÇÕES PATOLÓGICAS EM EDIFICAÇÕES EM ALVENARIA ESTRUTURAL NO MUNICÍPIO DE BELO HORIZONTE
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Advisor : FLAVIO ANTONIO DOS SANTOS
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COMMITTEE MEMBERS :
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FLAVIA SPITALE JACQUES POGGIALI
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FLAVIO ANTONIO DOS SANTOS
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PETER LUDVIG
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WHITE JOSE DOS SANTOS
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Data: Feb 9, 2018
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The construction industry is one of the sectors that employ in Brazil and has a significant share in the Gross Domestic Product (GDP). One of the reasons for this participation may be linked to financial incentives from the Federal Government, through mortgage loans. The works that use structural masonry represent most of the financing of the mortgage plan Caixa Economica Federal. This system is presented as an alternative to completion of works with reduced costs, with higher profit possibilities for builders. However, to get a satisfactory result, ensuring the quality of the buildings, it is necessary to the effective control of the components and the execution of the works, following a well-designed project. Failure to comply with the standards in each of these steps may cause the appearance of pathological manifestations, compromising the expected performance of the enterprise and reducing its useful life. In this context, student work of these manifestations in buildings in structural masonry located in Belo Horizonte city. Through building inspections, the main constructive problems and their next causes were identified, with the purpose of proposing future actions that avoid these types of pathological manifestations. It was possible to observe that the lack of adequate planning was one of the main factors that contributed to the emergence of these problems. Although not posing an immediate risk to building structures, these problems cause discomfort and mistrust to the residents and may have more serious consequences during building’s service life.
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9
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FELIPE SERGIO BASTOS JORGE
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INFLUÊNCIA DA CINZA DE CASCA DE ARROZ COMO ADIÇÃO MINERAL NO COMPORTAMENTO MECÂNICO DE CONCRETO COM FIBRAS DE AÇO
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Advisor : CONRADO DE SOUZA RODRIGUES
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COMMITTEE MEMBERS :
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CONRADO DE SOUZA RODRIGUES
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FLAVIO DE ANDRADE SILVA
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PAULO HENRIQUE RIBEIRO BORGES
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Data: Feb 16, 2018
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Concrete has high compressive strength and durability, but its ductility is low, which makes it a brittle material with little capacity for energy absorption, or toughness. In this sense, research with fibers incorporated in concrete has been directed with the objective of adding toughness. In cement-based composites, the interfacial transition zone (ITZ) is one in which the first cracks arise which, when propagated, lead to a material failure. The performance of fiber reinforced cement-based composites depends on stress transfer process efficiency to fibrous reinforcement, in order to guarantee the assembly operation. Among the determinants of this efficiency is the quality of cementitious matrix that is given by its density, that is, as interface between materials becomes dense, the adhesion between these components increases. Mineral additions have been incorporated into cement matrixes with two fundamental objectives: to give a sustainable destination to agroindustrial waste and to improve cement-based composites properties. Rice husk ash (RHA), which is produced by burning rice hulls for energy generation purposes, has a high content of amorphous silica, which gives it high potential for its pozzolanic activity. The objective of this research was to evaluate the effects of the incorporation of steel fibers and RHA in concretes whose formulation is used in railway lines production. For this, characterization tests of fresh and hardened concrete currently used in production were carried out, four-point flexural tests on the fiber-reinforced concretes in the percentages of 0.5, 0.75 and 1.0% with and without RHA and single fiber pullout tests in propositions with and without RHA. The results showed gains in load peaks, residual resistance post-cracking and toughness. Use of RHA proved to be effective and is a good alternative for increasing the properties of reinforced concrete with steel fibers.
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10
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João Luiz Guerra Freire
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STRUCTURAL CHARACTERIZATION OF AN OVERHEAD CRANE BY THEIR MODAL PARAMETERS
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Advisor : CLAUDIO JOSE MARTINS
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COMMITTEE MEMBERS :
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CLAUDIO JOSE MARTINS
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PETER LUDVIG
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RENATA GOMES LANNA DA SILVA
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WALNORIO GRACA FERREIRA
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Data: Feb 20, 2018
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The objective of this study is the structural characterization of a liquid steel transport overhead crane, with 120 tons of capacity on the main car, 30 tons in the auxiliary car and 22,5 m free span; by its modal parameters such as natural frequencies, damping rates and modes of vibration.
The experimental modal parameters of the crane structure were obtained from the recording of its vibrations in a real situation, by measurements of piezoelectric accelerometers. Its structural characterization will be obtained by adjusting the modal values of a numerical model based on the Finite Element Method to the experimental values.
In order to validate the technique, the results will also be compared through numerical simulation of the topographic measurement and extensometry tests. Through this results comparison, it is expected to evaluate quantitatively the difference between the values obtained with the modal analysis results and the usual static tests of deflectometry and extensometry.
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11
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Felipe Carvalho Silva Santos
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OPERATIONAL MODAL ANALYSIS OF MONTESE VIADUCT: FINITE ELEMENT MODEL UPDATING AND COMPARISON WITH STATIC LOAD TEST.
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Advisor : CLAUDIO JOSE MARTINS
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COMMITTEE MEMBERS :
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CLAUDIO JOSE MARTINS
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RENATA GOMES LANNA DA SILVA
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ELIENE PIRES CARVALHO
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WALNORIO GRACA FERREIRA
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Data: Feb 20, 2018
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Operational Modal Analysis is a methodology widely used in order to identify structural modal parameters without interrupting its use. In civil structures, this methodology is used along with a finite element model, which allows structural health monitoring, and damage detection besides of determination of how existent pathology affects structural performance.
In the present work, the Montese Avenue’s viaduct Operational modal analysis is presented. Acceleration was measured in 16 points over superstructure in three orthogonal directions in a 50Hz sampling rate resulting in a 40 hours of measured data. It was employed SSI-COV algorithm in order to identify structure’s natural frequencies. A finite element model of the structure was developed to be calibrated with the frequencies resultants of the modal analysis. This model is going to be tested with a simulation of a static load test, which was performed in the viaduct before traffic liberation.
Both models calibration’s was successfully done. Errors in frequencies are small for several modes, but some modes presented frequencies errors above 10%. Despite static load test simulation results diverge from structural response, we considered model behavior improvement satisfactory due to input data quality.
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12
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Ricardo Perim Real
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Assessment of the use of rice husk ash as a mineral admixture in high performance concrete.
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Advisor : NILTON DA SILVA MAIA
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COMMITTEE MEMBERS :
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CONRADO DE SOUZA RODRIGUES
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FLAVIA SPITALE JACQUES POGGIALI
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JOÃO BATISTA SANTOS DE ASSIS
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NILTON DA SILVA MAIA
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Data: Feb 21, 2018
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High performance concrete (HPC) is a special type of concrete that has better mechanical properties and durability over conventional concretes, without damaging the material properties in its fresh state (workability). In addition to the traditional components of the concrete, when producing HPC, mineral admixtures and chemical additives are used to improve the microstructure of the material and ensure good workability even at lower water/cement ratios. Rice husk ash (RHA) is an agricultural residue whose use as a mineral admixture in concrete has been studied and explored recently. The theoretical review presented in this study shows the great amount of studies developed by the scientific community on the use of this agricultural byproduct. In order to evaluate this use, the present study proposes a series of tests that will be performed on cylindrical specimens (10 x 20 cm) of HPC with levels of cement substitution by the residue of 10% to 20% by mass. The tests will evaluate the behavior of the concrete in its fresh state (slump test) and in its hardened state (modulus of elasticity, compressive strength, water absorption, mercury intrusion porosimetry and rapid chloride permeability test), in order to investigate rheological, mechanical and durability properties. A pilot study, whose results are presented in this qualification proposal, performed the physicochemical characterization of the HPC constituent materials, with emphasis on mineral admixture (chemical composition, granulometry, density, surface area, morphology and mineralogical composition). In addition to this characterization, preliminary tests (slump test, modulus of elasticity and compressive strength) were performed in specimens with the same dosage as those that will be produced in the final study, however, with the use of plasticizer additive and upper water/cement ratio. The results were satisfactory and indicate the behavior expected of the concrete in the final study, when a superplasticizer additive and a lower water/cement ratio will be used.
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13
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DANIELLE STÉFANE GUALBERTO FERNANDES
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AVALIAÇÃO DA ADERÊNCIA ENTRE BARRAS FINAS DE AÇO E CONCRETOS DE DIFERENTES CLASSES DE RESISTÊNCIA
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Advisor : ELIENE PIRES CARVALHO
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COMMITTEE MEMBERS :
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ELIENE PIRES CARVALHO
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RENATA GOMES LANNA DA SILVA
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CLAUDIO JOSE MARTINS
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EDGAR VLADIMIRO MANTILLA CARRASCO
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Data: Mar 6, 2018
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Show Abstract
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A aderência aço-concreto é um mecanismo de interação que possibilita a transferência de esforços das barras de aço para o concreto. Ela se mostra como uma das propriedades fundamentais em elementos de concreto armado. Para avaliação da aderência aço-concreto, verificou-se, na literatura, que os ensaios mais utilizados são: ensaios de arrancamento, ensaios de vigas rotuladas e ensaios de barras confinadas. Estudos anteriores apontam que o ensaio de barras confinadas mostra-se inadequado para barras finas de aço e que o ensaio de vigas rotuladas apresenta difícil execução. Já o ensaio de arrancamento mostra-se como o mais simples e utilizado dos métodos para estudo do comportamento da aderência. No entanto, existem poucas pesquisas que adotaram os ensaios de arrancamento para barras finas de aço (diâmetros de até 10,0 mm), que são normalmente utilizadas na construção civil, devido ao emprego cada vez maior do concreto de alta resistência e de elementos esbeltos. A norma brasileira ABNT-NBR 7480 (2007) requer um ensaio de aderência para controle de qualidade das barras. Portanto, atualmente há uma preocupação com os resultados dos ensaios para avaliar a aderência açoconcreto, principalmente para barras finas de aço. Dessa forma, o principal objetivo deste trabalho foi o estudo da aderência entre barras nervuradas finas (6,3 mm, 8,0 mm e 10,0 mm) e concretos convencional e de alta resistência (30 MPa e 60 MPa). Procurou-se, com esta pesquisa, contribuir para compreender melhor o comportamento da aderência aço-concreto para barras finas de aço e fornecer informações importantes para a definição de padrões futuros para ensaios de aderência. Para tanto, foram realizados ensaios de arrancamento de acordo com a EN:10080 (2005), adotando-se um comprimento de ancoragem modificado de 10 vezes o diâmetro da barra. Os resultados dos ensaios indicaram que, para barras finas, o diâmetro da barra não teria influência na tensão última de aderência e que esta aumentaria com o aumento da resistência à compressão do concreto. Quanto ao comprimento de ancoragem adotado, são necessários mais ensaios para conclusões a respeito desse parâmetro. Em relação ao coeficiente de conformação superficial (η), os resultados apontaram valores próximos, independente do diâmetro ou da classe de concreto.
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14
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FRANCISCO ARISTIDES DOS SANTOS NETO
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PARÂMETROS DE FRATURA DE PASTAS DE CIMENTO FABRICADO COM NANOTUBOS DE CARBONO
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Advisor : PETER LUDVIG
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COMMITTEE MEMBERS :
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PETER LUDVIG
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JUNIA NUNES DE PAULA
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ROBERTO BRAGA FIGUEIREDO
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JOSÉ MÁRCIO FONSECA CALIXTO
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Data: Apr 25, 2018
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View Dissertation/Thesis
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Show Abstract
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Apesar de sua ampla utilização na construção civil, os compósitos cimentícios se caracterizam pela baixa resistência à tração, capacidade de absorção de energia e por se apresentarem suscetíveis à microfissuras geradas pelas retrações e/ou atuações de cargas. Essas características são consideradas deficiências críticas que além de gerarem limitações ao projeto estrutural podem afetar a durabilidade das estruturas. Para superar essas deficiências o reforço através da aplicação de micro- ou macrofibras é comumente empregado. Contudo, os compósitos cimentícios apresentam falhas em escala nanométrica, na qual esse reforço tradicional não é eficiente. Devido às suas excelentes propriedades mecânicas, como a alta resistência à tração e capacidade de deformação, os nanotubos de carbono são ótimos candidatos para reforçar os materiais cimentícios, inibindo a iniciação e a propagação dessas falhas e melhorando as propriedades mecânicas dos compósitos cimentícios. No presente trabalho, utilizou-se um clínquer nanoestruturado com nanotubos e nanofibras de carbono (NTC/NFC), sintetizado in situ e de maneira contínua, para preparar compósitos de pastas de cimento e investigar os comportamentos mecânicos de fratura dessas pastas avaliando os resultados de resistência à tração na flexão, a energia de fratura e a tenacidade à fratura. Além da pasta de cimento referência, foram fabricadas pastas de cimento com 0,10%, 0,20% e 0,30% de NTC/NFC em relação ao peso do cimento. O ensaio de flexão em três pontos e o método de Correlação Digital de Imagem (CDI) foram empregados simultaneamente durante o ensaio das pastas de cimento nanoestruturadas – aos 7, 28 e 120 dias de idade – para colher os dados para análise. Os testes estatísticos ANOVA e Tukey foram empregados para auxiliar na avaliaçãodos resultados,os quais mostraram que a incorporação do clínquer nanoestruturado nas pastas de cimento proporcionou ganhos nas propriedades mecânicas avaliadas, especialmente aos 7 dias de idade das pastas.
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15
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Carla Milagros Espinal Rodriguez
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Perception and evaluation of the soundcape in urban areas. Case study at the Municipal Park Américo Renné Giannetti in Belo Horizonte
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Advisor : MARIA CRISTINA RAMOS DE CARVALHO
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COMMITTEE MEMBERS :
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MARIA CRISTINA RAMOS DE CARVALHO
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CONRADO DE SOUZA RODRIGUES
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SIMONE QUEIROZ DA SILVEIRA HIRASHIMA
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MARCELA ALVARES MACIEL
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Data: May 8, 2018
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View Dissertation/Thesis
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Show Abstract
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A considerable part of the users of open urban spaces in main cities are exposed to high noise levels, which can negatively affect the health and the quality of life of the population. To reach a satisfactory level of acoustic comfort in urban spaces, besides compliance with technical standards and relevant legislation, evaluations of the sound environment, taking into account the context and the human perception, are also parameters that should be considered. The sound environment that is perceived by an individual in a given context is called soundscape. The perception of environmental sounds can vary between individuals, resulting uncomfortable for some and a pleasant sound for others. The aim of this work is to study the soundscape through the analysis of the perception of the users of the Américo Renné Giannetti Municipal Park in Belo Horizonte, as well as students of architecture and urbanism who have studied the acoustics discipline to define criteria for the evaluation of the acoustic comfort of the space. To this end, acoustic and microclimatic measurements were taken, as well as interviews with the use of forms addressed to users of the space, and questionnaires intended for students, to be answered at different sampling points within the park. This data was later analyzed and treated generating layers of information. As results, it is expected to analyze the perception of the park's soundscape, comparing the user's responses also in each of the stations. The collected data can be mapped, presenting graphically the points of highest sound quality and the most degraded points acoustically, putting in evidence the perception of the sound environment in the park, which may be useful for the elaboration of guidelines aimed at improving the sound quality in this urban space.
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16
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Kastelli Pacheco Sperandio
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Application of the ground penetrating radar to riks area (landslide) in belo horizonte – MG
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Advisor : HERSILIA DE ANDRADE E SANTOS
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COMMITTEE MEMBERS :
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HERSILIA DE ANDRADE E SANTOS
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REMKE LEANDER VAN DAM
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FELIPE DE MORAES RUSSO
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PAULO ROBERTO ANTUNES ARANHA
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Data: May 22, 2018
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View Dissertation/Thesis
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Show Abstract
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In the area of engineering, knowing the characteristics and conditions of the soil is essential to understand and predict their behavior during the works carried out, as a way to ensure their safety. The definition of the geological, geotechnical and geomorphological characteristics of the subsoil is fundamental, among many purposes, for the understanding and prevention of accidents such as landsliding, since these characteristics, together with pluviometric factors and anthropic actions, are considered the main causative factors of these accidents present in periods of intense and prolonged rainfall in Brazil. Among many methods and equipment that have emerged in recent years to characterize the soil, one has stood out for its efficiency and ease of application in the most diverse situations: the Ground Penetrating Radar (GPR). This geophysical research technique, which consists of the emission and capture of high frequency electromagnetic waves through antennas located on the surface, to obtain images of high resolution of the subsurface presents high potential to aid in the prevention of accidents involving landslides. In this context, the present work proposes to use GPR in soil characterization of a slope located in the city of Belo Horizonte, aiming to develop a preventive methodology to be applied in areas with risk of landslide. The soil characterization is composed by the results of laboratory tests on the samples collected at the site, percussion drilling (SPT) and geophysical tests using GPT. In order to determine the frequency of antennas and the methodology to be used, preliminary tests with GPR of 100 MHz and 200 MHz frequency were performed in two of the profiles defined for the study site. Due to the intense noise present at the site it was not possible to define the ideal antenna frequency for the site, since the radargrams resulting from these preliminary tests are not of good quality. Possibly the interferences generated in the data come from a high voltage tower located near the study site, and then new preliminary tests are necessary, after the strategy change in order to reduce these interferences, so that the studies can be continued. It is expected at the end of the work that quantitative (laboratory and survey) and qualitative (use of GPR) assessments converge to the possibility of being able to state whether or not the site is under threat of landslide.
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17
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SCARLET NATALIE JORGE PEGUERO
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AVALIAÇÃO DO PROCESSO DE IMPLEMENTAÇÃO DA TRANSIÇÃO DOS SISTEMAS DE GESTÃO DA QUALIDADE ISO 9001 versões 2008 e 2015 - EMPRESAS DA CONSTRUÇÃO CIVIL
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Advisor : ROGERIO CABRAL DE AZEVEDO
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COMMITTEE MEMBERS :
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ROGERIO CABRAL DE AZEVEDO
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HERSILIA DE ANDRADE E SANTOS
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DANIELA MATSCHULAT ELY
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ADRIANO DE PAULA E SILVA
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Data: May 23, 2018
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View Dissertation/Thesis
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Show Abstract
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The implementation of quality management systems certified according to the ISO 9001: 2008 standard together with the Brazilian Program for Quality and Productivity in Habitat (PBQP-H) are the most commonly used tools used by construction companies to manage quality. The latest revision of the ISO 9001 standard that guides the deployments was published in the year 2015. The introduction of new processes to be integrated in the already existing systems, as well as the loss of the validity of the certifications in September 2018, generated that the construction companies initiated roadmaps of implementation of these new procedures. During the follow-up of the implementation roadmaps, there are aspects that may facilitate or hinder the incorporation of the new procedures in the quality management systems still in force within the companies of the sector such as the motivations that drive the system upgrade, and the critical success factors. Few studies in recent years study these aspects exclusively for the Brazilian construction industry. This paper aims at evaluating the motivations, understanding of the standard by companies and the critical success factors or barriers that may occur during the process of implementing the new requirements introduced in ISO 9001: 2015. In response to these objectives, this research intends to describe these aspects using a questionnaire as a means of collecting data. It is hoped that this research will find the motivations that drive companies to adopt the new processes included in the last revision of the standard published in the year 2015, the relation of the type of motivation, and the degree of difficulty that companies have to implement the new processes and critical success factors or barriers that may hinder or facilitate the implementation process.
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18
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INÁCIO SANTIAGO DE OLIVEIRA QUEIROZ
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Development of ultra high strength concrete using locally available materials from the northern region of Minas Gerais
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Advisor : PETER LUDVIG
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COMMITTEE MEMBERS :
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PETER LUDVIG
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CONRADO DE SOUZA RODRIGUES
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ADRIANA GUERRA GUMIERI
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Data: Jul 9, 2018
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View Dissertation/Thesis
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Show Abstract
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Ultra High Strength Concrete (UHSC) is ranked among the most advanced concrete technologies. The UHSC allows more challenging works, with great potential and architectural value, providing an esthetic value to the buildings or special structures. UHPC technologies raise the interest of the prefabricated concrete industry as a basis material for modern construction methods. The costs involved in manufacturing this material, in line with the high consumption of cement per m3, limit the expansion of production at scale. The use of local materials, by-products of the production of silicon metal, promotes the proper destination of by-products and reduces the cost of the production of such concretes. The use of new technologies in the execution of concrete structures can lead to direct gains, such as reduction of concrete volume, reduction of steel consumption and higher execution speed, requiring less living work hours, and indirect gains, such as reduction of impacts, design flexibility and reduction of the cross section. The performance of the UHSC is strongly influenced by the optimization of the packing of particles, that is, the better this packaging, the greater the degree of compactness and the effective performance of the concrete. The objective of this work is to compare the mechanical properties of the UHSC, in the fresh and hardened state, produced with three different types of Portland cement, using active silica and quartz powder, from the northern region of Minas Gerais, with different types of cure. It was possible to achieve compressive strength above 200 MPa with thermal cure and above 170 MPa with wet curing at 28 days. The Modified Andreassen method was used for the packing of particles with the factor q = 0.32.
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19
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Nelson Rafael Muñoz Matos
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Gestão de facilidades em tempo real: Integração da visão computacional no BIM
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Advisor : MARIA CRISTINA RAMOS DE CARVALHO
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COMMITTEE MEMBERS :
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MARIA CRISTINA RAMOS DE CARVALHO
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FLAVIO ANTONIO DOS SANTOS
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FLAVIO LUIS CARDEAL PADUA
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DANIELLE MEIRELES DE OLIVEIRA
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Data: Jul 9, 2018
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View Dissertation/Thesis
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Show Abstract
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The construction industry is currently suffering from low productivity, resulting a deficiency to service basic infrastructure development, of which the country relies upon for economic growth. Studies have found that technologic innovation is needed as one of the basic cornerstones for sustainable growth and productivity. The use of Building Information Modeling (BIM) in the construction industry has emerged as one of the main tools for responding to this technologic innovation need, bringing the construction process as well as the whole building live-cycle into the age of integrated information. Another technology that has shown great success is Computer Vision (CV) applied to BIM in order to digitally reproduce in real-time the construction progress and state. Facilities Management (FM) represents a crucial element of the industry that has not seen the application of these two technologies in conjunction in the same way they have been applied in other industry segments. This work has the objective of studying the viability of integrating VC with BIM for capturing, processing and visualizing data to facilitate the operation and decision-making processes of FM. This is achieved through data gathering about various CV techniques that can be used in conjunction with BIM for FM. The data gathering consists of researching existing academic literature, as well as operational reports and conducting interviews with industry professionals. The collected data is subsequently classified and graphically mapped in a coherent conceptual structure, and this resulting structure is validated once more with industry experts. This validated structure is used to produce a conceptual framework and it is applied to the creation of a prototype of the technology which will be used for test cases against security camera datasets, the results of which will be validated with the industry once again. It can be proven that the developed technology is a viable alternative to facilitate a more efficient FM, which at the same time reuses security cameras without the addition of sensors or the increase in costs typically associated with traditional data gathering and sensing systems.
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