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Tokudome, Shingiro. "Contribuição para o desenvolvimento do concreto auto-adensavel." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258503.
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Orientador: Vladimir Antonio PaulonDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil
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Resumo: A presente dissertação tem como objetivo o desenvolvimento da especialidade da tecnologia do concreto de elevado desempenho, o concreto auto-adensável. A tendência do mercado em construir cada vez mais estruturas arrojadas exige o desenvolvimento de tecnologias que coadunem com a realidade técnico-econômica da obra. A concretagem destas estruturas, quando realizada em formas irregulares e em armação densa, ocasiona, na maioria das vezes, problemas no adensamento, formando descontinuidade e/ou segregação na peça concretada. Contudo, quando executada em concreto auto-adensável, estas ocorrências tendem a diminuir. Este trabalho apresenta a confrontação da metodologia de avaliação do concreto autoadensável no estado fresco com o método da caixa L e o utilizado atualmente na Alemanha conforme a norma DIN 1045 -2 DAfStb- Richtlinie Selbstverdichtender Beton (SVB-Richtlinie), com o propósito de levar para a prática procedimentos simples e de fácil análise do controle de trabalhabilidade do concreto, e também a aplicação do concreto auto-adensável em estruturas de escala real para analisar a segregação do concreto quando lançados a 4,00 metros de altura.
Abstract: This study concerns a special kind of high performance concrete technology development, called self-compacting concrete. The growing market tendency to build bold structures requires construction technology development, which fits real technical-economical needs. The concrete placing in irregular shape structures, and reinforced concrete structures, most of time brings compacting problems and result on segregation, and/or not satisfactory concrete surfacing. However, the use of self-compacting concrete can reduce these problems. The main objective of this research is to compare L box method and the German standard DIN 1045 -2 DAfStb- Richtlinie Selbstverdichtender Beton (SVB-Richtlinie) for fresh self compacting concrete workability analysis, in order to propose the L box method as an practical and easy way test to control the fresh concrete quality. This study also provides an accurate description of self-compaction concrete history, its development and the advantages reached by the structures based on concrete selfcompacting concrete, as well. Furthermore this research sets a real beam and column structure concrete applications from 4,00 m high filling to analyze segregation behavior.
Mestrado
Edificações
Mestre em Engenharia Civil
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Ferraz, Andre Luiz Nonato. "Avaliação de retração e fluencias do concreto auto-adensavel para aplicação em elementos pre-moldados." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/257677.
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Orientadores: Newton de Oliveira Pinto Junior, Monica Pinto BarbosaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
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Resumo: Foram avaliados neste trabalho, teórica e experimentalmente, o comportamento reológico e mecânico do concreto auto-adensável (C.A.A.), em específico suas características frente as deformações lentas, retração e fluência, e sua aplicabilidade em peças pré-moldadas. Foram desenvolvidos duas composições de concreto de classes de resistência distintas, 35 e 55 MPa. Na etapa de dosagem foram utilizados os procedimentos do método REPETTE-MELO, onde nas pastas e argamassas, foram realizados ensaios reométricos, ensaios de fluidez e Mini-Slump, e na definição do traço do C.A.A., ensaios de controle, tais como Slump-Flow, Funil em V, caixa em L, caixa em U e tubo em U, assim como ensaios das propriedades mecânicas tais como resistência à tração, resistência à compressão, e módulo de elasticidade. A avaliação do comportamento dos concretos frente a fluência se deu nas idades de 7, 14, 28, e 56 dias, segundo a NBR 8224 (ABNT, 1983), e frente a retração de acordo com a norma MERCOSUL NM 131:9. Os resultados experimentais foram comparados com valores de concretos convencionais disponíveis na literatura. Todos os ensaios foram realizados no Laboratório CESP de Engenharia Civil, e no Laboratório de Hidrologia da UNESP em Ilha Solteira-SP. No estudo da deformação rápida, ensaios de tração na flexão foram realizados aos 28 e 56 dias. Os coeficientes de fluência foram calculados quer seja através dos valores experimentais como pela NBR 6118 e comparados entre si, apresentando boa correlação, com diferenças menores que 10% para toda as idades. A composição do concreto auto-adensável foi implantada para fins de avaliação, junto a empresa de Pré- Moldados Protendit de São José do Rio Preto-SP, onde foram moldadas vigas, em escala real, as quais apresentaram melhor acabamento e se mostraram 50% mais economicas, em relação a mão-de-obra, quando comparada com a viga de concreto convencional. Os resultados obtidos mostram que as composições de concreto auto-adensável apresentam maiores valores de retração e fluência quanto comparados com concretos convencionais de mesma resistência mecânica. O C.A.A. de resistência à compressão igual a 55 MPa apresentou menor retração e fluência básica que o C.A.A. de resistência 35 MPa.
Abstract: This project analyzed, theoretically and experimentally, the mechanical and rheological behavior of the selfcompacting concrete (C.A.A.), specially its features according to slow deformation, shrinkage and creep, and its applicability in precast elements. Two compositions of concrete of different classes of resistance were developed, 35 MPa and 55 MPa. In the stage of the dosage, the procedures of the method REPETTE-MELO were used, rheometrical tests, fluidness tests and Mini-Slump were carried out on the pastes and the mortars, and control tests, such as Slump-Flow, funnel V test, box L, box U and tube U, and mechanical properties tests, such as tensile strength, compression strength and elasticity module were used to define the C.A.A. feature. The evaluation of the concrete behavior by creep happened at ages of 7, 14, 28, and 56 days, according to NBR 8224 (ABNT, 1983), and by shrinkage according to MERCOSUL NM 131:9. The experimental results were compared with values from conventional concrete available in the literature. All tests were performed at CESP Civil Engineer Laboratory, and at Hydrology Laboratory of the UNESP in Ilha Solteira-SP. In the fast deformation study, traction tests in flexion were performed at 28 and 56 days. The creep coefficients were calculated either through experimental values as by the NBR 6118 and compared each other, showing a good correlation, with differences smaller than 10% for all ages. The composition of self-compacting concrete was established for evaluation, in partnership with precast elements company Protendit of São José do Rio Preto-SP, where were shaped beams, in real scale, which showed better finishing and they showed themselves 50% more economical regarding labor, when compared with conventional concrete beam. The results reached show that the compositions of self-compacting concrete present higher values of shrinkage and creep when compared with conventional concrete of same strength. The C.A.A. that presented compression strength equal to 55 MPa showed a lower shrinkage and basic creep that C.A.A. strength of 35 MPa.
Doutorado
Edificações
Doutor em Engenharia Civil
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Bekoe, Patrick Amoah. "Concrete containing recycled concrete aggregate for use in concrete pavement." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0025075.
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Bolognini, Enio José [UNESP]. "Idealizações de um programa baseado em redes neurais para dosagem de concreto." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/144535.
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A produção de concreto está cada vez mais exigente. Medidas de prevenção e correção são empregadas na dosagem do concreto, gerando lucros e economia no preparo. A fim de obter economia e praticidade na dosagem de concretos, neste estudo foi desenvolvido, após a coleta de dados experimentais, a criação de rede neural artificial feedforward, utilizando algoritmo genético de retropropagação (backpropagation). A rede neural artificial (RNA) é composta de quatro camadas, entre entradas, pesos, bias, função de ativação sigmóide e saída desejada. O modelo conta com funções sigmoides, a fim de calcular e otimizar o erro através das camadas anteriores, até a entrada. Este modelo, por ser mais preciso, conta com certo momento e taxa de aprendizagem. A proposta da rede neural artificial (RNA) em feedforward, com o algoritmo genético de retropropagação (backpropagation), foi implementada em forma estrutural, e com uma interface gráfica, na qual o usuário final possa escolher a resistência desejada, tipo de cimento, tipo e dimensão de agregados graúdos, dimensão de agregados miúdos, tipo de concreto e aditivo, se for o caso de concretos de alta resistência (CAR). Nesta pesquisa, a coleta de dados, para armazenar no programa, foi realizada por meio de ensaios de caracterização dos materiais e de dosagem e resistência do concreto. A linguagem de programação Java foi utilizada para programar o algoritmo genético e a interface usuário. Foram realizados os testes e manutenção da ferramenta computacional, seguindo regras importantes no desenvolvimento de softwares. O resultado final, deste desenvolvimento, foi um software capaz de calcular a dosagem do concreto para o usuário, quando este insere valores de resistência à compressão axial desejada e o material que será usado na confecção do concreto.
The concrete production is increasingly demanding. preventive and corrective measures are used in concrete dosage, generating profits and savings in preparation. In order to achieve economy and practicality in the dosage of concrete in this study was developed after the collection of experimental data, the creation of artificial neural network feedforward using genetic algorithm backpropagation. The artificial neural network (ANN) is composed of four layers, between inputs, weights, biases, sigmoid activation functions and output desired. The model has sigmoid functions in order to calculate and optimize the error by the preceding layers, until the entrance. This model, to be more precise, has the right time and learning rate. The proposed artificial neural network (ANN) in feedforward, with the genetic algorithm backpropagation, was implemented in structural form, and with a graphical interface, in which the end user can choose the desired strength, cement type, and size of coarse aggregates, fine aggregates dimension, type of concrete and additives, if any of high strength concrete (CAR). In this research, data collection, to store the program, was carried out by means of characterization tests of materials and dosage and strength of concrete. The Java programming language was used to program the genetic algorithm and the user interface. testing and maintaining software tool were conducted following important rules in the software development. The end result of this development was an able to calculate the dosage of specific software for the user, when it enters resistance values to the desired axial compression and the material that will be used in the manufacture of concrete.
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Bolognini, Enio José. "Idealizações de um programa baseado em redes neurais para dosagem de concreto /." Ilha Solteira, 2016. http://hdl.handle.net/11449/144535.
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Orientador: Maria da Consolação Fonseca de AlbuquerqueResumo: A produção de concreto está cada vez mais exigente. Medidas de prevenção e correção são empregadas na dosagem do concreto, gerando lucros e economia no preparo. A fim de obter economia e praticidade na dosagem de concretos, neste estudo foi desenvolvido, após a coleta de dados experimentais, a criação de rede neural artificial feedforward, utilizando algoritmo genético de retropropagação (backpropagation). A rede neural artificial (RNA) é composta de quatro camadas, entre entradas, pesos, bias, função de ativação sigmóide e saída desejada. O modelo conta com funções sigmoides, a fim de calcular e otimizar o erro através das camadas anteriores, até a entrada. Este modelo, por ser mais preciso, conta com certo momento e taxa de aprendizagem. A proposta da rede neural artificial (RNA) em feedforward, com o algoritmo genético de retropropagação (backpropagation), foi implementada em forma estrutural, e com uma interface gráfica, na qual o usuário final possa escolher a resistência desejada, tipo de cimento, tipo e dimensão de agregados graúdos, dimensão de agregados miúdos, tipo de concreto e aditivo, se for o caso de concretos de alta resistência (CAR). Nesta pesquisa, a coleta de dados, para armazenar no programa, foi realizada por meio de ensaios de caracterização dos materiais e de dosagem e resistência do concreto. A linguagem de programação Java foi utilizada para programar o algoritmo genético e a interface usuário. Foram realizados os testes e manutenção da ferramenta com... (Resumo completo, clicar acesso eletrônico abaixo)
Mestre
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Ore, Andrade Harold Oscar Rosil, and Diaz Miguel Angel Portillo. "Propuesta de diseño de mezcla para un concreto permeable de FC=175kg/cm² en veredas." Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2019. http://hdl.handle.net/10757/635423.
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El Perú presenta diversas eventualidades como las lluvias, que retrasan distintas actividades que promueven el crecimiento económico del país. Las zonas urbanas necesitan una mejora continua del entorno con mejores infraestructuras para promover el crecimiento y reducir los accidentes. En la actualidad, se necesita fomentar por el medio local soluciones innovadoras para la evacuación de altas precipitaciones.
El concreto permeable es un tipo de concreto cuya tecnología permite que el agua discurra a través de su estructura por la alta porosidad que posee a diferencia del concreto tradicional. Es fabricado de agregado grueso y material cementante, con un bajo porcentaje de finos de hasta el 10%.
Esta investigación consiste en proponer un diseño de mezcla de concreto permeable de f’c=175kg/cm² aplicado en veredas que satisfaga distintos requerimientos establecidos por las normas CE010 de Pavimentos Urbanos, ACI 211.3R, ACI 522R-10 y los propios de la zona de aplicación. Para ello se realizó una batería de 12 diseños de mezcla con relaciones a/c 0.30, 0.35 y 0.38; agregados de HUSO 7 y 67; cementos portland tipo 1 Sol y Quisqueya; y aditivo Z fluidizante SR. Se realizaron ensayos en estado fresco: Slump, peso volumétrico y contenido de vacíos; y en estado endurecido: Resistencia a la compresión y flexión, y permeabilidad. Finalmente se realizó un prototipo con el diseño que presentó mejores características con el propósito de validar la investigación y se realizo un comparativo entre las veredas de concreto permeable y tradicional.Peru presents various eventualities such as rainfall, which delay different activities that promote the country's economic growth. Urban areas need continuous improvement of the environment with better infrastructure to promote growth and reduce accidents. At present, innovative solutions for the evacuation of high rainfall need to be promoted through the local environment. Permeable concrete is a type of concrete whose technology allows water to flow through its structure due to the high porosity it possesses, unlike traditional concrete. It is made of coarse aggregate and cementitious material, with a low percentage of fines of up to 10%. This research consists in proposing a permeable concrete mix design of f'c = 175kg / cm² applied in sidewalks that satisfies different requirements established by the CE010 standards of Urban Pavements, ACI 211.3R, ACI 522R-10 and those of the area of application. For this, a battery of 12 mixing designs with a / c ratios of 0.30, 0.35 and 0.38; aggregates of HUSO 7 and 67; portland cements type 1 Sol and Quisqueya; and fluidizing Z additive SR. Fresh tests were performed: Slump, volumetric weight and void content; and in a hardened state: resistance to compression and flexion, and permeability. Finally, a prototype was made with the design that presented better characteristics with the purpose of validating the research and a comparison was made between the permeable and traditional concrete sidewalks.
Tesis
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Rosa, Alaor Leandro. "Estudo da influência da taxa de solicitação na resposta em fratura quase-frágil." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258103.
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Orientador: José Luiz Antunes de Oliveira e SousaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
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Resumo: A pesquisa objeto desta tese refere-se a uma investigação dos processos de fratura no concreto de alta resistência (High Strength Concrete - HSC), com ênfase no estudo da influência da taxa de carregamento (medida como a taxa de deslocamento do ponto de aplicação de carga) nos ensaios de fraturamento e assim caracterizar sua ductilidade em tração. Neste trabalho um modelo de fratura dependente do tempo (modelo coesivo-viscoso) é apresentado e a influência da taxa de carregamento na resposta em fratura quase-frágil é estudada através de simulação numérica. O modelo de fratura dependente do tempo acopla um parâmetro viscoso, dado em função da velocidade de abertura da fratura, ao modelo clássico de fissura fictícia proposto por Hillerborg, tal que uma relação tensão-abertura de fissura dependente do tempo, (?, ?), represente uma zona coesiva-viscosa inserida em um meio elástico não-viscoso. O modelo coesivo-viscoso é implementado no arcabouço teórico do método dos elementos finitos com um método de cálculo iterativo que modela a fratura quase-frágil (comportamento não-linear) como uma superposição de problemas em mecânica da fratura elástica linear (Linear Elastic Fracture Mechanics - LEFM). O modelo numérico implementado é validado com os resultados experimentais obtidos de vigas prismáticas ranhuradas em flexão em três pontos (Three-Point Bend Test - TPBT), com taxas de carregamento variando da ordem de = 10-5 mm/s a 6 = 10+1 mm/s. Os resultados numéricos obtidos mostram que o modelo coesivo-viscoso implementado, apesar de sua simplicidade, reflete o fato experimentalmente documentado de que a nucleação e a propagação de uma fratura coesiva, bem como os fenômenos que governam os processos de fratura, são dependentes da taxa de carregamento. Assim, a diferença obtida por muitos pesquisadores na medida da energia de fratura não se deve unicamente à escala do protótipo ensaiado mas também à taxa de carregamento aplicada nos ensaios.
Abstract: This thesis addresses a numerical investigation to account for loading rate influence (measured as the load-point displacement rate) on the fracture processes of quasi-brittle materials such as high strength concrete (HSC). In this context, fracture tests are simulated by a proposed time-dependent cohesive model. The proposed model couples a viscous parameter, as a function of crack-opening rate, to the classical Hillerborg's fictitious crack approach such that a time-dependent stress crack opening law, (?, ?), represents a viscous-cohesive zone in an elastic, time-independent, body. The viscous cohesive representation is implemented in a finite element framework using a iterative method in such a way that the equations governing the quasebrittle crack propagation (non-linear behaviour) is sought from a triangular system of equations, obtained by superposing linear elastic fracture mechanics (LEFM) cases. To show the accuracy of the model, numerical simulations of notched beams in three-point bend test (TPBT) were performed. In the tests five different loading rates were employed (ranging from = 10-5 mm/s = 10+1 mm/s). The results numerically obtained match very well the experimental ones, particularly the maximum load for the several loading rates used in the tests. A parametric study has also been performed to point out which are the model, geometry and fracture parameters influencing the fracture process due to loading rate. The numerical results show that the model, although its simplicity, provides a general approach to reflect the experimentally documented fact that crack propagation and so the parameters governing the fracture processes in cementious materials depend on the loading rate. So, the differences obtained by several researches worldwide on the fracture energy measurement are not only due to the scale of the tested specimens, but also due to the loading rate influence.
Doutorado
Estruturas
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Souza, Adriana Aparecida Ambrosio de 1975. "Procedimento de ensaio para verificação em laboratório da tendência ao lascamento do concreto em situação de incêndio." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258256.
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Orientador: Armando Lopes Moreno JúniorTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
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Resumo: O lascamento é um fenômeno complexo, estocástico, e que pode causar um efeito danoso a estruturas de concreto em situação de incêndio. O fenômeno do lascamento deve, portanto, ser considerado no projeto de construções em que a ação do fogo é levada em conta. Não existe um procedimento de ensaio normalizado para avaliação da tendência ao fenômeno do lascamento do concreto. Os resultados de outros pesquisadores mostram diferentes procedimentos, tamanho das amostras, preparo das amostras (execução e cura), tempo de exposição à temperatura, evolução da temperatura ao longo do tempo (taxas de elevação), quantificação do fenômeno (degradação das amostras em termos de fissuração e desprendimento de camada superficial das amostras), o que dificulta comparação dos resultados obtidos. Esta pesquisa apresenta um procedimento de ensaio para avaliar a tendência ao lascamento de misturas de concreto em situação de incêndio e mostra que este fenômeno está relacionado, principalmente, ao tipo de agregado utilizado e a umidade do concreto exposto à elevadas temperaturas. Como resultado pôde - se observar que um concreto preparado com agregado calcáreo apresenta maior lascamento de superfície, do que um concreto preparado com agregado basalto, mesmo este apresentando fissuração superficial. Ao final, concluí - se que o procedimento proposto é eficaz na avaliação e determinação do tipo de dano causado
Abstract: The spalling is a complex phenomenon, that may cause a damage effect on concrete structures in a fire situation. The spalling phenomenon should, therefore, be considered in the constructions design, in that the fire effect is taking account. It does not exist a standardization of tests proceeding for evaluation of spalling phenomenon tendency in concrete. The results of others researchers show different proceedings, specimens size, specimens preparation (execution and cure), fire resistance, temperature evolution in a time period, phenomenon amount (degradation of specimens about its cracking and come unstuck of superficial layer of the specimens), what make difficult the comparison of the obtained results. This research shows a test proceeding to evaluate the spalling tendency of concrete mixing under fire situation and also shows that this phenomenon is mainlly relating to the aggregate type used and to the concrete humidity under high temperatures. As a result it could observed that a concrete made with calcareous coarse aggregate shows higher surface spalling than a concrete made with basaltic coarse aggregate, even this specimen of concrete showing a superficial cracking. At the end, it did conclude that the proposal proceeding is efficient in the evaluation and determination of the damage
Doutorado
Estruturas
Doutor em Engenharia Civil
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Catoia, Thiago. "Concreto ultraleve® estrutural com pérolas de EPS: caracterização do material e estudo de sua aplicação em lajes." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-19122012-104222/.
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A utilização de concreto leve decorre especialmente dos benefícios promovidos pela redução da massa específica do material, tais como menores esforços nas estruturas, economia com fôrmas e cimbramento, além de diminuição dos custos com transporte e montagem de construções pré-fabricadas. Atualmente, além das questões técnicas e econômicas, a escolha dos materiais de construção deve levar em conta os aspectos ambientais. Portanto, o uso de poliestireno expandido (EPS) na produção de concreto pode abrir portas para o emprego de resíduos de materiais dessa natureza, e ainda usufruir de sua baixa massa específica nas aplicações estruturais. Este trabalho teve como objetivo determinar as principais características do concreto leve com pérolas (esferas) de EPS, também conhecido como Concreto Ultraleve® ou Concreflex®, características essas necessárias para projetar elementos estruturais, e analisar o comportamento de lajes produzidas com esse novo material. Mais especificamente, foram determinadas características mecânicas, tais como: resistência à compressão, módulo de elasticidade e resistência à tração, na compressão diametral e na flexão, além de características de deformação de longo prazo, como retração e fluência. Também foi determinada a massa específica e avaliada sua relação com as características mecânicas, além dos ensaios de modelos de lajes unidirecionais produzidas com esse concreto. Para analisar a possibilidade de aplicação prática do concreto leve com EPS em lajes, foram elaboradas tabelas para pré-dimensionamento de lajes unidirecionais e bidirecionais com o novo material, nas quais essas lajes foram comparadas com as de concreto comum. Com base no procedimento experimental e nos resultados dos ensaios, o objetivo de determinar as características necessárias para projetar elementos estruturais de Concreto Leve com EPS foi alcançado. Pode-se ainda afirmar que o concreto estudado, com aproximadamente metade da massa específica dos concretos convencionais, apresenta características compatíveis com a produção e o uso comercial de lajes maciças, principalmente pré-moldadas, o que pode ser estendido a outros elementos que não necessitem de concretos com resistência muito alta. Também foi avaliado o comportamento de modelos de lajes de concreto leve com poliuretano (PU), de maneira semelhante ao estudo realizado com EPS, incluindo a caracterização do concreto de cada modelo. Para complementar a análise de desempenho do concreto leve com EPS, apresentou-se um estudo de carbonatação, que comprovou a excelente condição desse novo material com relação à durabilidade.The use of lightweight concrete is mainly due to the benefits provided by reducing the density of the material such as smaller efforts on structures, economy of molds and scaffolding, as well as lower costs of transportation and erection of precast constructions. Currently, besides the technical and economic issues, the choice of building materials should take into account environmental aspects. Therefore, the use of expanded polystyrene (EPS) in the concrete production can open doors for the use of waste materials of this nature, and still to take advantage of its low density in structural applications. This study aimed to determine the main characteristics of the lightweight concrete with EPS beads (spheres), also named Ultra Lightweight Concrete, characteristics which are necessary to design structural members, and analyze the behavior of slabs produced with this new material. More specifically mechanical properties were determined, such as compressive strength, modulus of elasticity, and splitting and flexural tensile strength, as well as long term deformation properties such as shrinkage and creep. The density was also determined and evaluated its association with the mechanical characteristics, besides the tests of unidirectional slab models produced with this concrete. To analyze the possibility of use of the lightweight concrete with EPS in slabs, tables were compiled for pre-design of unidirectional and bidirectional slabs with this new material, in which these slabs were compared with those of common concrete. Based on the experimental procedure and results of tests, the aim of determine the characteristics necessary to design structural elements of lightweight concrete with EPS has been achieved. Can be also said that the studied concrete, with about half the density of conventional concrete, presents mechanical characteristics compatible with commercial production and use of slabs, mainly precast, conclusion which can be extended to other components that do not require concretes with very high strength. It was also assessed the behavior of slab models of lightweight concrete with polyurethane (PU) in a similar way to the study carried out with EPS, including the characterization of concrete for each model. To complement the performance analysis of the lightweight concrete with EPS a study of carbonation was presented, which proved the excellent condition of this new material with respect to durability.
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Lannon, Kristyna Tylova. "Using recycled concrete aggregate in pervious concrete." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0025119.
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FARIA, Ricardo Andrade Fernandes. "CONTRIBUIÇÃO AO ESTUDO DAS PROPRIEDADES MECÂNICAS E DA DURABILIDADE DE CONCRETOS COM ESCÓRIA DE ACIARIA ELÉTRICA (EAF) COMO AGREGADO GRAÚDO." Universidade Federal de Goiás, 2007. http://repositorio.bc.ufg.br/tede/handle/tde/674.
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Previous issue date: 2007-10-17The increasing demand for aggregate for uses in engineering stimulated the search for alternative materials. In this way, the civil construction potentially started to be a great consumer of residues from other industries, becoming a great recycle plant. The use of by-product, brings great environmental benefits in relation to the degradation of the environment, as for example, less settlement of residues in earth fill, the reduction of extraction of natural resources, and the exploration of aggregate ores. Steel plants from around the world have a commom problem, that is what to do with all the steel slags generated as a by-product from the steel refining in electric steel plants or oxygen steel plants. There are two points of these process where slags can be generated: the first comes from the electric or oxygen furnace itself (called oxidizing refining) and the second is the laddle metallurgy slag (reduction refining slag), which is the last stage of the steel production. This aims to demonstrate related studies to the use of steel slags (EAF slags) in electric steel plants as coarse aggregate. Expansibility of the steel slag tests had been carried through, compressive strength, tensile strength for diametrical compression, related modulus of deformation and durability tests, such as: intensity of corrosion, potential of corrosion, ohmic resistivity and depth of carbonation. After this, it was observed the similarity of the results between the concrete made with steel slag and the concrete made with conventional aggregates, natural aggregate known as mica schist. It was observed improvements in the properties of the concrete with steel slag, such as: increase in its strength (compressive / tensile) and increase of the modulus of deformation. Concerning the durability, it was noted, in a general way, that the substitution of the aggregates, conventional for siderurgical, has not influenced in the performance of the concrete.
A crescente demanda por agregados para usos em engenharia estimulou a procura por materiais alternativos. Desta forma, a construção civil passou a ser potencialmente uma grande consumidora de resíduos provenientes de outras indústrias, tornando-se uma grande usina recicladora. A utilização de subprodutos traz benefícios ambientais bastante expressivos em relação à degradação do meio ambiente, como por exemplo, a menor deposição de resíduos em aterros, a diminuição da extração predatória de recursos naturais e a exploração de jazidas de agregados. As siderúrgicas, em nível mundial, vêm enfrentando um problema comum, que consiste no que fazer para que a totalidade da escória gerada no refino do aço em aciarias elétricas ou a oxigênio tenha uma solução de aproveitamento melhor do que vem sendo feito atualmente. Na fabricação do aço as escórias são geradas em duas etapas: a primeira provém do chamado refino oxidante (forno elétrico a arco ou convertedor à oxigênio) e a segunda do refino redutor em processos de metalurgia na panela (forno-panela). Este trabalho tem como objetivo específico demonstrar, por meio de estudos, a potencialidade do uso das escórias de aciaria elétrica (escórias FEA) como agregado graúdo. Foram realizados ensaios de expansibilidade, resistência à compressão, à tração por compressão diametral, módulo de deformação e ensaios relacionados à durabilidade, tais como: intensidade de corrente de corrosão, potencial de corrosão, resistência ôhmica e profundidade de carbonatação. Após o estudo realizado observou-se a semelhança dos resultados dos concretos confeccionados com escória de aciaria elétrica com os concretos confeccionados com agregados convencionais, no caso o micaxisto. Podem-se constatar melhorias nas propriedades dos concretos produzidos com escória, tais como: aumento em suas resistências (compressão / tração) e aumento do módulo de deformação. No que diz respeito à durabilidade verificou-se, de uma maneira geral, que a substituição dos agregados, convencional por siderúrgico, não influenciaram no desempenho dos concretos.
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Nunes, Nelson Lúcio. "Contribuição para a aplicação do concreto reforçado com fibras de aço em elementos de superfície restringidos." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/3/3146/tde-04052006-170328/.
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Este trabalho apresenta um estudo para a previsão de comportamento quanto à fissuração e seu controle pelo uso das fibras de aço, em elementos de superfície de concreto restringidos, ou seja, submetidos às tensões de tração induzidas pela retração restringida. Neste estudo, foi desenvolvido um método analítico para calcular o consumo de um determinado tipo de fibra de aço em função do potencial de retração da matriz de concreto e da máxima abertura de fissura, determinada em função de parâmetros de durabilidade e aceitabilidade sensorial. Posteriormente, foram realizados ensaios para caracterização do potencial de fissuração de matrizes de concreto utilizadas em obras de elementos de superfície, onde testou-se um método de estimativa das tensões induzidas por retração restringida no concreto, no momento da primeira fissura. Na etapa final do trabalho, foi realizado um programa experimental, com a construção de pistas de concreto reforçado com fibras de aço (CRFA), com consumos de fibras de 10 kg/m3, 30 kg/m3 e 60 kg/m3, construídas sobre bases com duas condições de restrição: superfície desempenada e superfície jateada com exposição dos agregados. A fissuração destas pistas, nas primeiras idades, foi monitorada através da medida da abertura e do comprimento das fissuras. Com os resultados desta etapa experimental, foi realizada uma retroanálise do método onde concluiu-se que a consideração de valores característicos na previsão da resistência à tração do concreto era um ajuste necessário e coerente com a observação prática. Com o ajuste, os resultados experimentais de abertura de fissura ficaram dentro da faixa de previsibilidade do método, considerando um intervalo de confiança de 90%. Com o desenvolvimento deste método, buscou-se contribuir para a aplicação do CRFA no controle da fissuração por retração restringida de elementos de superfície, ampliando a fronteira do conhecimento no aspecto da escolha e dosagem da fibra para um determinado desempenho esperado quanto à fissuração.This work presents a study for crack prediction and use of steel fibers to crack control in concrete surface elements submitted to tension stress induced by restrained shrinkage. In this study, a method was developed where a certain steel fiber type could be quantified, as function of concrete matrix shrinkage potential and maximum crack width, determined from human sensorial and durability criteria. Afterwards, an experimental program was done in order to characterize the crack potential of concrete matrices commonly used in surface elements. In this program, a method to predict tension stress induced by restrained shrinkage, at first crack moment, was tested. In the final step of this work, another experimental program was done, where steel fiber reinforced concrete (SFRC) tracks were built, with fiber contents of 10 kg/m3, 30 kg/m3 and 60 kg/m3, over substrates with two restriction conditions: smooth surface and rough surface, with exposition of surface aggregates. Lengths and widths of the early age shrinkage cracks in the tracks were monitored. The results obtained in this program were useful to analyze the method, adjusting it with the consideration of characteristic values in prediction of tension strength. With this adjust, experimental crack width results were more compatible with 90% confidence interval for crack width values predicted by the method. With this study, the goal was the contribution to use SFRC in the control of restrained shrinkage cracks in surface elements, amplifying the knowledge border in the aspect of fiber selection and proportioning, for a determined and expected performance in terms of crack width.
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Miranda, Centeno Cristian Arturo, and Moreno Marco Eduardo Rado. "Propuesta de concretos reforzados con fibras de acero y cemento puzolánico para la construcción de pavimentos rígidos en la región de Apurímac." Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2019. http://hdl.handle.net/10757/628106.
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La finalidad de la investigación realizada en este documento es presentar el concreto reforzado con fibras de acero como alternativa de solución para la construcción de pavimento rígido. La necesidad de mejorar la calidad de los pavimentos rígidos frente a los problemas recurrentes de fisuración, optimizar costos, aumentar la calidad y optimizar los materiales para mejorar la sostenibilidad ambiental y social, impulsa el estudio e investigaciones sobre distintos aditivos que se agregan al concreto como también el tipo de refuerzo que lo complementa.
Este documento se enfocará en realizar una propuesta de concretos reforzados con fibra de acero y cemento puzolánico para la construcción de pavimento rígido comparando las propiedades físicas y mecánicas de las mezclas y así obtener la mezcla más eficiente que cumpla las condiciones del expediente técnico para así realizar la aplicación en un tramo del proyecto de pavimentación en la provincia de Grau del departamento de Apurímac.The purpose of the research carried out in this document is to present concrete reinforced with steel fibers as technical solution for the construction of concrete pavement an alternative solution for the construction of rigid pavement. In order to save costs per cubic meter per square meter of pavement and optimize raw material so increase quality and optimize materials to improve environmental and social sustainability, encourages the study and research on different chemical addition that are added to the concrete as well as the type of reinforcement that complements it. This document will focus on making a proposal of reinforced concrete with steel fiber and pozzolanic cement for the construction of rigid pavement by comparing the physical and mechanical properties of the mixtures and thus obtain the most efficient mixture that meets the conditions of the technical file in order to perform the application in a section of the paving project in the province of Grau of the department of Apurímac.
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Matos, Lucas Henrique Lozano Dourado de. "Pavimentos intertravados de concreto utilizando resíduos de PET /." Ilha Solteira, 2019. http://hdl.handle.net/11449/180816.
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Orientador: Cesar Fabiano FioritiResumo: O crescimento da população e do seu poder aquisitivo mudaram a geração de resíduos. Atualmente se produz resíduos diferentes em qualidade e volume diferentes daqueles produzidos por gerações passadas. Entre os resíduos gerados atualmente se encontram os resíduos de PET, oriundos de embalagens descartáveis, que acarretam problemas ambientais devido ao descarte incorreto. Este trabalho se propõe em estudar a aplicação destes resíduos para a produção de pavers de concreto, observando suas características de desempenho em relação aos pavers produzidos com concreto convencional, ambos produzidos por procedimentos manuais. Para atingir o objetivo proposto foram realizados ensaios de trabalhabilidade, ensaios de massa específica em estado fresco e endurecido, ensaios de absorção de água, medição da incorporação de ar, ensaios de resistência à compressão, tração e impacto e microscopia eletrônica de varredura para os traços produzidos com 5%, 10%, 15% e 20% de substituição em volume dos agregados miúdos e graúdos. Dessa maneira, foi possível buscar informações a respeito do comportamento obtido por meio da substituição parcial dos agregados pelos resíduos de PET produzindo peças com características semelhantes àquelas proporcionadas pelos pavers convencionais, atingindo a resistência à compressão de 35 MPa, definida em norma, em 4 traços produzidos, mesmo com valores de absorção superiores aos 6% estipulados em norma.
Abstract: Population growth and purchasing power changed waste generation. Currently the wastes produced differs in quality and volume than that produced by past generations. Amongst the waste currently produced are the PET waste, originating from disposable packaging, which generate environmental problems due to incorrect disposal. The purpose of this work is to study the application of these residues in concrete pavers production, observing the performance characteristics in comparison to those produced with conventional concrete, both produced by manual procedures. To achieve the proposed goal were performed workability tests, specific weight in both fresh and hardened conditions, water absorption tests, air content tests, compressive strength, splitting tensile strength and impact tests and scanning electron microscopy for the concrete designs containing 5%, 10%, 15% and 20% by volume of both fine and coarse aggregate. Thus, it was possible to achieve information about the concrete behavior produced with partial substitution of the aggregates by the PET waste, producing pavers with similar characteristics of those provided by pavers produced with conventional concrete, achieving the compressive strength of 35 MPa, required by standard, in 4 mixtures with substitution, although the absorption values were above the 6% required by standard.
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Dumêt, Tatiana Bittencourt. "Aderência de cordoalhas em concretos de alta resistência com e sem fibras de aço." Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-18042016-113235/.
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Este trabalho apresenta os resultados das investigações teórica e experimental sobre a aderência de cordoalhas pré-tracionadas, em concretos de alta resistência com e sem fibras de aço. Foram utilizadas cordoalhas de sete fios com Φp 12,7 mm e fibras de aço curtas, com ganchos nas extremidades (DRAMIX) e fator de forma 1/d=45. Foram realizados dois tipos de ensaios: arrancamento e flexão em viga. Os parâmetros estudados foram: comprimento de ancoragem (5Φp, 7Φp e 15Φp), volume de fibra (zero, 40 kg/m3 e 60 kg/m3 e grau de protensão (zero e 0,8fptk). O concreto apresentou resistências à compressão de 50 MPa no momento da transferência da protensão e 68 MPa na data de ensaio, aproximadamente. Os resultados dos dois tipos de ensaio foram analisados e comparados com as prescrições normativas da NBR 6118 (2001), da FIB Bulletin 1 (1999) e do ACI 318 (2002), onde verificou-se que as prescrições se encontram a favor da segurança. A conclusão principal resultante desta pesquisa foi que a utilização de fibras com 40 kg/\'m3 por metro quadrado não influi na aderência. Já para um volume de fibra de 60 kg/\'m3 por metro quadrado há um ganho de aproximadamente 28% na aderência, em relação aos concretos sem fibras de aço, nos ensaios de arrancamento. Para as vigas, não houve ganho de aderência para os volumes de fibra utilizados, nem na determinação do comprimento de transferência, nem na do comprimento de ancoragem necessário.This study presents the results of a theoretical and an experimental investigation of the bond of pretensioned strands embedded in plain and steel fiber reinforced high strength concrete. There were used seven wires strands with 12,7 mm diameter and short hooked steel fibers with an aspect ratio of 1/d=45. Two types of tests were carried out to obtain the bond characteristics of the strands: pullout tests and beam under flexure tests. The parameters studied were the volume fraction (0%, 0,51% and 0,76%) of the fibers, and the degree of prestress of the strand (zero and 0,8fptk). The concrete compressive strength was 50 MPa at transfer (3 days of age) and 68 MPa at 28 days of age (test date), approximately. The results were analyzed and compared to the provisions of the following Codes: NBR 6118 (2001) (Brazilian code under public consult), ACI-318 (2002) and FIB-Bulletin 1 (1999). The comparison indicated that the codes give a safe design. The main conclusion of this work was that the use of 0,5% of steel fibers does not influence the bond strength of the strand. The use of 0,76% of steel fibers increases the bond stress in 28% when compared with plain concrete, for the pullout tests. For the beam\'s tests there was no bond improvement due to the steel fibers, in both case (0,5% and (0,76%), neither for the transfer length nor for the development length.
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Silva, Valdirene Maria. "Ação da carbonatação em vigas de concreto armado em serviço, construídas em escala natural e reduzida." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-19032007-100952/.
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Este trabalho apresenta uma análise do comportamento da frente de carbonatação em vigas de concreto armado sob tensão, em escala natural e reduzida, com a máxima condição de subarmação. As vigas foram construídas com e sem adição da sílica da casca de arroz e sílica de ferro silício ou silício metálico. Para cada viga em escala natural (agregado graúdo com D máx. = 19 mm) foi moldada uma em escala reduzida com o mesmo traço de concreto para estabelecer os mesmos parâmetros de comparação. As vigas foram curadas durante 7 dias e posteriormente submetidas à flexão, com o carregamento aplicado nos terços (L/3 da viga). Realizou-se o pré-condicionamento para a estabilização da umidade interna das vigas que foram expostas durante 28 dias em um ambiente com concentração de 50% de dióxido de carbono, umidade relativa de 65 \'+ OU -\' 5% e temperatura ambiente. Foram determinados: resistências à compressão simples axial, resistência à tração por compressão diametral, módulos de elasticidade e profundidade da frente de carbonatação em corpos-de-prova cilíndricos. A profundidade da frente de carbonatação em corpos-de-prova foi determinada para diferentes concentrações de dióxido de carbono. Também foi verificada a carbonatação ao longo das vigas em escala natural e reduzida e nas posições das fissuras. Para a previsão da profundidade da frente de carbonatação nas vigas, foram ajustadas equações para a representação da carbonatação na região das fissuras. Os resultados obtidos mostraram a eficiência da espessura do cobrimento, a eficácia dos modelos físicos reduzidos para realizar estudos de carbonatação e a tendência da carbonatação em elementos estruturais na condição de serviço. A frente de carbonatação difere na posição das fissuras, evidenciando um comportamento diferente quando comparado com corpos-de-prova. A análise microestrutural ilustrou o comportamento da frente de carbonatação em vigas de concreto armado, complementando o estudo experimental. Com base nos resultados obtidos pode-se afirmar que a simples adoção de concretos de alto desempenho para construção de elementos estruturais não é suficiente nas peças que contenham fissuras e que sejam submetidas a atmosferas ambientais agressivas.This work reports on the behavior of carbonation in reinforced concrete beams under stress regime on full and small scales having the lowest possible frame. The beams were made with and without adding silica from rice husk and silica fume (Fe-Si). For each beam on a full scale (coarse aggregate with D máx. = 19 mm) another beam on a small scale was made with the same mix of concrete to maintain the same comparison parameter. The beams were cured for 7 days and subsequently submitted to flexure by applying a two-point loading (L/3 of beam). Humidity stabilization to stabilize internal humidity of beams exposed for 28 days in an environment with a concentration of 50% carbon dioxide, 65 \'+ OR -\' 5% of relative humidity and room temperature was carried out. The following was determined: axial compression strength, tensile splitting strength, young\'s modulus and carbonation depth in cylindrical specimens. The carbonation depth was determined in specimens with unlike carbon dioxide concentration. Moreover, carbonation along beams on full and small scales and in cracks was observed. To estimate the carbonation depth of the beams, equations were adjusted to represent the carbonation in cracks. The results show the efficiency in the thickness of the cover, efficiency of small-scale models for studies concerning carbonation and behavior of carbonation in the serviceability of structural elements. The carbonation depth differs in the position of cracks, showing behavior which is unlike the one compared to specimens. The microstructure analyses show the behavior of carbonation depth in reinforced concrete beams complementing the experimental study. The results show that it is not sufficient to use high performance concretes in structural elements for elements with cracks and in aggressive atmospheres.
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Pinheiro, Brunno Antonio Onofre. "Pisos industriais de concreto reforçados com fibras de aço: estado da arte." Universidade Católica de Pernambuco, 2009. http://www.unicap.br/tede//tde_busca/arquivo.php?codArquivo=1112.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorO concreto reforçado com fibras de aço é um material compósito, onde o concreto é a matriz e o reforço são as fibras. No Brasil ele começou a ser utilizado na década de 90, e atualmente é uma das soluções mais eficientes para os pisos industriais, que são estruturas muito importantes, pois se constituem na base de toda a produção. Um problema nesses pisos pode significar prejuízos financeiros na ocorrência de interrupção das atividades industriais. Foram estudadas algumas fibras utilizadas como adição para o concreto, em especial as de aço. Foram abordados os principais tipos de pisos de concreto, com ênfase nos reforçados com fibras de aço, suas características, interações fibra x matriz, parâmetros de eficiência, controle de qualidade, principais patologias e terapias, bem como carregamentos atuantes e critérios de dimensionamento. Concluiu-se que as fibras de aço desempenham importante papel no controle de propagação das fissuras, aumentando a ductilidade da placa e a tenacidade, podendo até aumentar a capacidade portante da estrutura dependendo do volume de fibras empregado.
The steel fiber reinforcement concrete is a composite material. The concrete is the matrix and the reinforcement are fibers. In Brazil, it started to be used in the decade of 90, and nowadays its one of the most efficient solution for industrial floors, witch are very important structures because the whole production consists on it. A problem with these kind of floors is that it creates financial damages in the occurrence of interruption of industrial activities. Some fibers had been studied as an addition to the concrete, mostly the steel ones. The main types of concrete floors had been boarded, with emphasis on the reinforced with steel fiber, looking for its characteristics, interactions fiber x matrix, efficiency parameters, quality control, main pathologies and therapies, as well as existent loads and dimensions. It was concluded that the fiber steel performance has an important role in the control of propagation of the cracks, increasing the residual strength factors, even being able to increase the capacity of the structure, depending on the volume of fiber steel that is applied.
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Azevedo, Pedro Ribeiro. "Confinamento dado por vigas e lajes a pilares feitos com concretos de diferentes resistências ao longo da altura." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/3/3144/tde-22102014-165727/.
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Para melhor aproveitamento da resistência do concreto, utiliza-se concreto de maior resistência à compressão em pilares e concreto de resistência inferior em vigas e lajes. Considerando o método construtivo adotado tradicionalmente no Brasil, a região do pilar que cruza o nível do pavimento é moldada com a utilização do mesmo material que é lançado no pavimento. Essa mistura de materiais no mesmo pilar gera dúvida em relação ao seu dimensionamento. Dado que essa região está confinada pelo pavimento pode-se considerar, no caso em que uma laje lisa circunda o pilar, dentro de determinados limites, que esse pilar se comportará como tendo resistência uniforme. Este trabalho levantou pesquisas anteriores e normas vigentes com o objetivo de saber o que já foi estudado e quais são as recomendações atuais para a situação em que se tem laje apoiada sobre vigas e não uma laje lisa, isto é, uma situação menos confinada. Com base nessa pesquisa, formularam-se modelos a serem ensaiados em escala reduzida no laboratório e modelos de elementos finitos com a finalidade de aprofundar o estudo dessa situação.Aiming the better use of the concrete strength a high-performance concrete is use in columns and a less resistant concrete in slabs and beams. Considering the constructive method adopted in Brazil, the region of the column that crosses the floor is executed using the same material that is used at the pavement. When used in columns, it is blended with a less resistant concrete in the floors, which is not considered during the column design. Is it possible that this less resistant concrete can confine the column to the point that its strength turns out to be the same of the rest of the members? This paper has studied earlier researches and up-to-date standards with the goal of know what have been studied and the actual recommendations for situations that the floor has beams and slabs instead of only slabs, in other words, a less confined region. Based in this research was formulated models to be tested in the laboratory and models in Finite Element Models to studie further the stresses.
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Christ, Roberto. "Desenvolvimento de compósitos cimentícios avançados à base de pós-reativos com misturas híbridas de fibras e reduzido impacto ambiental." Universidade do Vale do Rio dos Sinos, 2014. http://www.repositorio.jesuita.org.br/handle/UNISINOS/3207.
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itt Performance - Instituto Tecnológico em Desempenho da Construção Civil
O desenvolvimento de novos concretos vem sendo ampliado ao longo dos anos, o que ocorre paralelamente ao aprimoramento dos cálculos estruturais e ao maior conhecimento sobre as propriedades dos materiais, o que conduz os projetistas ao desenvolvimento de estruturas que necessitam ter características específicas. Com isso surge a necessidade de se desenvolver concretos especiais, que apresentam elevada resistência mecânica e durabilidade. O concreto de pós reativos, também chamado de CPR, é um exemplo destes materiais. Trata-se de um concreto de ultra alto desempenho, com elevada resistência mecânica, extremamente dúctil e de baixa porosidade. Este tipo de concreto apresenta propriedades mecânicas superiores em comparação aos concretos de alta resistência, chegando a resistências à compressão de 200 MPa, à tração de 45MPa e módulo de elasticidade superior a 50 GPa. O consumo de cimento neste tipo de concreto pode atingir 800 kg/m3, além de incorporar elevado volume de sílica ativa. A otimização granular dos constituintes, realizada através de métodos de empacotamento de partículas, faz com que seja possível obter um material com o mínimo de vazios e elevada densidade. As fibras introduzidas no composto proporcionam elevada ductilidade. Neste trabalho, parte do cimento Portland foi substituído por cinza volante, para desenvolver um CPR com baixo consumo de aglomerantes. Também foi estudada a incorporação de dois tipos de fibras, ou hibridização, para uma matriz de CPR com menor consumo de cimento. A introdução de dois tipos distintos de fibras proporciona ao material maior sinergia, diminuindo a formação e a propagação de fissuras durante o carregamento. Os resultados obtidos nesta pesquisa mostram que a substituição parcial do cimento por cinza volante apresentou melhor desempenho mecânico, atingindo resistência à compressão de aproximadamente 190 MPa com 30% de adição. A incorporação de dois tipos distintos de fibras, aço e polipropileno em teores de 80% e 20% respectivamente, proporcionou ao material elevada resistência à tração na flexão e tenacidade. Portanto, é possível dosar CPR com menores consumos de cimento e uso de dois tipos de fibras, melhorando as propriedades da mistura e obtendo um compósito com reduzido impacto ambiental.
The development of new concretes is being expanded over the years, withal the improvements in structural design, along the increased knowledge of materials properties, which leads the designers to develop structures with specific requirements. It arises the need of the development of special concretes, with have enhanced mechanical strength and durability. Reactive powder concrete, also called RPC, is an example of these materials. This is an ultra-high-performance concrete with high mechanical strength, extremely ductile and low porosity. This type of concrete has superior mechanical properties compared to high strength concrete, reaching compressive strengths of 200 MPa, tensile strengths of 45 MPa and modulus higher than 50 GPa. The cement consumption in this type of concrete may reach 800 kg/m3, while incorporating high volumes of silica fume. The optimization of granular constituents accomplished by particle packing methods provides a material with a minimum of voids and also high density. The fiber introduced into the material compound provides high ductility. On this report, fly ash was used to replace some part of the cement, aiming the development of a RPC with low agglomerate consumption. It was also studied the use of two types of fiber, or hybridization, to a RPC matrix array of CPR with less consumption of cement. The introduction of two distinct types of fibers gives the material improved synergy, decreasing the formation and propagation of cracks during the charging. The results obtained in this study show that the partial replacement of cement by fly ash gives better mechanical performance, reaching the compressive strength of approximately 190 MPa with 30% addition. The incorporation of two different types of fibers, steel and polypropylene at levels of 80% and 20% respectively, provided the materials high tensile strength and toughness. Therefore, it is possible to compose an RPC with lower cement consumption and use of two types of fibers, improving the properties of the mixture and obtaining a composite with reduced environmental impact.
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Shimosaka, Tobias Jun. "Influência do teor de diferentes tipos de fibras de aço em concretos autoadensáveis." Universidade Tecnológica Federal do Paraná, 2016. http://repositorio.utfpr.edu.br/jspui/handle/1/2303.
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CAPESO emprego de concreto em estruturas é bastante elevado em todo o mundo. Entretanto, o concreto convencional pode apresentar problemas relacionados com a durabilidade da estrutura, como o caso dos vazios de concretagem. O concreto autoadensável (CAA), vem se caracterizando como uma evolução do concreto convencional, pois apresenta vantagens como capacidade de preencher espaços, devido a auto adensabilidade, elimina falhas de concretagem e possibilita estruturas mais duráveis. Apesar dessas melhoras no estado plástico, no estado endurecido, as características do CAA se assemelham muito com as de um concreto convencional, ou seja, boa resistência à compressão, porém baixa resistência à tração e à fadiga. Assim, como forma de mitigar essas limitações, tem-se como evolução o emprego de concretos reforçados com fibras (CRF), os quais pela interferência da fibra atuando como costura nas fissuras presentes, resultam em compósitos, com melhor desempenho frente a esses esforços. Dentro desse contexto, a presente pesquisa analisou o desempenho de concretos autoadensáveis, com incorporação de fibras de aço, para que como resultado, fosse possível manter todas as melhoras ganhas no estado endurecido em suas propriedades mecânicas, sem que fossem perdidas as características de auto adensabilidade do CAA. Dessa forma, foram produzidas misturas, com diferentes tipos de fibras de aço (ancorada, corrugada e reta), com diferentes teores para cada tipo (0,4%, 0,8%, 1,2% e 1,5% em volume) e uma mistura de controle (sem adição de fibras), para então poder avaliar o comportamento do CAA quando incorporados diferentes tipos de fibras, com diferentes teores. A avaliação desse comportamento, se deu tanto no estado plástico do concreto, quanto no estado endurecido. Para as características no estado plástico, foram realizados os ensaios de espalhamento, t500 e Anel J. Para as propriedades no estado endurecido foram realizados ensaios de resistência à compressão axial, resistência à tração por compressão diametral, módulo de elasticidade. Além disso, buscou-se associar a resistência à fadiga do concreto, através de um ensaio não normatizado. Objetivando analisar a zona de transição, realizou-se o ensaio de microscopia eletrônica de varredura. Para analisar os resultados, foi necessário o emprego de tratamento estatístico, que avaliou a significância dos resultados. Os resultados mostram que foi possível manter a característica de auto adensabilidade do CAA para todos os teores de fibras empregados, e ainda obter ganhos, menos expressivos para resistência à compressão e de módulo de elasticidade, porém, resultados satisfatórios para resistência à tração e fadiga.
The use of concrete structures is fairly high throughout the world. However, conventional concrete can present problems related to the durability of the structure, as in the case of concrete voids. The concrete self compacting concrete (CAA), has been characterized as an evolution of conventional concrete, for advantages like ability to fill spaces through self adensabilidade eliminates concreting failures and enables more durable structures. Despite these improvements in the plastic state, in the hardened state, CAA characteristics closely resembling those of a conventional concrete, i.e., good compressive strength but low tensile strength and fatigue. Thus, in order to mitigate these limitations, we have to progress the use of reinforced concrete with fibers (CRF), which by the interference of the fiber acting as sewing in these cracks, result in composites with better performance against these efforts. In this context, the present study examined the self compacting concrete performance with the incorporation of steel fibers, so as a result, it was possible to keep all the improvements gained in the hardened state in their mechanical properties, without the self characteristics were lost adensabilidade CAA Thus, blends were produced with different types of steel fibers (anchored, and corrugated line), with different levels for each type (0.4%, 0.8%, 1.2% and 1.5% by volume ) and a mixture control (without fibers) and then to assess the CAA behavior when incorporated different types of fibers with different contents. The evaluation of this behavior occurred both in the plastic concrete state, as in the hardened state. For the characteristics in the plastic state, the scattering assays were performed, t500 and J. ring for the properties in the hardened state were performed resistance tests compressive, tensile strength by diametrical compression modulus. Furthermore, it sought to associate the fatigue strength of concrete, through a non-standardized assay. Aiming to analyze the transition zone, there was the scanning electron microscopy test. To analyze the results, employment was necessary statistical analysis, which evaluated the significance of the results. The results show that it was possible to maintain the characteristic of self adensabilidade CAA for all levels of employees fibers, and still obtain gains less significant compressive strength and modulus of elasticity, however, satisfactory results in tensile strength and fatigue.
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Torsvik, Øyvind André Hoff. "Pervious Concrete." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for konstruksjonsteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18665.
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Pervious concrete is a material with a high degree of permeability but generally low strength. The material is primarily used for paving applications but has shown promise in many other areas of usage. This thesis investigates the properties of pervious concrete using normal Norwegian aggregates and practices. An overview of important factors when it comes to designing and producing pervious concrete is the result of this investigation. Several experiments have been performed in the concrete research facility at NTNU, Trondheim.The importance of the void content of pervious concrete cannot be overstated. Too much void content leads to low strength while not enough void and permeability suffers and the concrete can hardly be called pervious. Proper design of pervious concrete is therefore largely dependent on finding the balance between strength and water permeability. The large interconnected voids in the material is achieved by using a near single sized aggregate of relatively large grains. The packing of this coarse aggregate leads to large voids due to the similar sizes of the grains. The amount of void left in the final concrete is then determined by how much binder is allowed to be mixed into the aggregates.Ten different batches of mortar has been produced with the intention of investigating the application of said mortars as the binder in pervious concrete. Six different batches of pervious concrete has been produced and tested for such properties as strength, permeability, density and void content. The goal of the experiments is to find and evaluate methods of determining the properties of pervious concrete. Mixing method of the material in addition to varying theoretical void content has been the focus of the experimental work.
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Miller, Nadine Lee. "Concrete impermanence." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0016/MQ52728.pdf.
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Rydberg, Dahlin Moa. "Concrete evolution." Thesis, KTH, Arkitektur, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122670.
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Den primära frågan i projektet har varit: Hur relaterar en tillbyggnad till den historia som en huvudbyggnad bär på? Resultatet är att den mest lämpade delen har växt ut, men anpassats för att rymma de funktioner som saknas i huvudbyggnaden. Min ambition har varit att få tillbyggnaden att både kännas som en naturlig del av Nationalmuseum och dess historia, samtidigt som den är ett eget kapitel. Den är både kopierande och hänsynslös. Var byggnaden skulle växa ut kom primärt av vad omgivningen skulle må bäst av. Vilken typ av vägg skulle ge de bästa uterummen? Rummet mot vattnet kommer att bli fantastiskt och rummet på andra sidan blir en förlängning av den idag väl fungerande lilla parken, med samma förutsättningar som denna. En studie av nationalmuseums travéstruktur generarade tankar kring hur byggnaden skulle kunna växa om man följde samma system. Den nya fasaden är en avgjutning av ett sådant travéavstånd (4427 mm) som upprepas. I denna fasad görs nya håltagningar för fönster, samt en portal för att möjliggöra flöden in och ut ur parken.The primary question of this project was: How does an add relate to what it´s added to? The result is that the most suitable part has grown, but adapted to accommodate the functions lacking in the main building. My ambition has been to get the building to be felt as a natural part of the National Museum and its history, as well as being a separate chapter. It is both replicating and reckless. How the building would grow is based of what the environment would benefit from. What type of wall would provide the best outdoor rooms? The room facing the water will be amazing and the room on the other side becomes an extension of the well-functioning small park, with the same conditions as this. A study of the National Museum trot structure made me think about how the building could grow following the same system. The new facade is a concrete "replica" (4427 mm) that is repeated. In this facade new holes are made for windows, and a portal to allow flows in and out of the park.
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Poellinger, Roland. "Concrete causation." Diss., Ludwig-Maximilians-Universität München, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-171789.
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Concrete Causation beschäftigt sich mit Theorien der Verursachung, ihrer Interpretation und ihrer Einbettung in metaphysisch-ontologische Fragestellungen sowie der Anwendung solcher Theorien in naturwissenschaftlichem und entscheidungstheoretischem Kontext. Die Arbeit gliedert sich in vier Kapitel, die eine historisch-systematische Verortung der zentralen Probleme vornehmen (Kapitel 1), um dann eine begriffliche und technische Darstellung der Theorien von David Lewis und Judea Pearl zu liefern (Kapitel 2). Der mathematisch-technische Rahmen von Pearl (in Bayes'schen Netzen) wird nach philosophisch motivierten begrifflichen Überlegungen für eine epistemische Interpretation von Kausalität und in einer Erweiterung des interventionistischen Ansatzes für die Betonung des wissensordnenden Aspekts von Kausalrelationen herangezogen (Kapitel 3). Die Integration von kausalem und nicht-kausalem Wissen in einheitlichen Strukturen stellt einen Ansatz zur Lösung von Problemen der (kausalen) Entscheidungstheorie dar und ermöglicht gleichzeitig die Abbildung von logisch-mathematischen, synonymischen sowie reduktiven Zusammenhängen in operationalisierbaren Netzen der Belief Propagation (Kapitel 4).Concrete Causation centers about theories of causation, their interpretation, and their embedding in metaphysical-ontological questions, as well as the application of such theories in the context of science and decision theory. The dissertation is divided into four chapters, that firstly undertake the historical-systematic localization of central problems (chapter 1) to then give a rendition of the concepts and the formalisms underlying David Lewis' and Judea Pearl's theories (chapter 2). After philosophically motivated conceptual deliberations Pearl’s mathematical-technical framework is drawn on for an epistemic interpretation and for emphasizing the knowledge-organizing aspect of causality in an extension of the interventionist Bayes net account of causation (chapter 3). Integrating causal and non-causal knowledge in unified structures ultimately leads to an approach towards solving problems of (causal) decision theory and at the same time facilitates the representation of logical-mathematical, synonymical, as well as reductive relationships in efficiently structured, operational nets of belief propagation (chapter 4).
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Zabihi, Nadia. "Concrete Exploration." Thesis, Konstfack, Industridesign, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:konstfack:diva-5974.
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Son, Sunghoon. "An investigation into the application of concrete, concrete additive and concrete reinforcement in contemporary sculpture." Thesis, University of Newcastle upon Tyne, 2008. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506507.
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Marques, Ana Carolina. "Concreto auto-adensável: caracterização da evolução das propriedades mecânicas e estudo da sua deformabilidade por solicitação mecânica, retração e fluência." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/3/3144/tde-08072011-160707/.
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O concreto auto adensável (CAA) é um material novo cujas propriedades mecânicas precisam ser estudadas. Ele apresenta em sua composição maior quantidade de argamassa e agregados graúdos de menores dimensões, que podem torná-lo mais deformável que o concreto convencional. Em contrapartida, o melhor empacotamento das partículas no estado fresco do CAA e a sua maior resistência (para uma mesma relação a/c) pode atuar no sentido oposto. Além disso, os modelos de previsão disponíveis na norma brasileira não levam em consideração os concretos especiais. O objetivo deste trabalho é verificar se modelos de previsão disponíveis na literatura são adequados para prever a fluência e a retração do CAA. Este estudo envolve aspectos de sua caracterização por meio de ensaios em laboratório, de retração, de fluência e de outras propriedades mecânicas como resistência à compressão, resistência á tração e módulo de elasticidade. Para o ensaio de fluência foram avaliadas as influências das condições ambientais (através de corpos de prova mantidos em ambiente controlado e sem controle de umidade e temperatura) e idade de carregamento. A partir dos resultados obtidos experimentalmente, foi feita a sua comparação com os modelos de previsão do ACI, EC2, NBR, B3 e GL. O estudo da deformação do CAA também foi feito por meio da monitoração de uma viga protótipo protendida, seguida da comparação das deformações medidas com as obtidas por um programa de elementos finitos. A partir dos resultados experimentais, observa-se que dentre os modelos de previsão de fluência e retração estudados, o que mais se adéqua aos resultados obtidos experimentalmente, é o fornecido pelo ACI e GL. A utilização do modelo de previsão do ACI pelo programa de elementos finitos gerou bons resultados de previsão de deformações quando comparados com os resultados medidos. Em relação à função de fluência, nota-se que a norma brasileira é adequada para o concreto estudado.Self-compacting concrete (SCC) is a new material and its mechanical properties have yet to be studied. It has a higher amount of mortar and smaller coarse aggregates which make it more deformable. On the other hand, the packing of the particles in fresh SCC and its larger strength (at a constant water/cement ratio) may act in the opposite way. Besides, the prediction models provided by the Brazilian Code do not take special concretes into account. The main objective of this work is to verify if the creep and shrinkage prediction models available in the literature can predict those properties of a SCC. This study involves aspects of its characterization by tests in laboratory of creep, shrinkage and other mechanical properties, such as compressive strength, splitting tensile strength and modulus of elasticity. For the creep test, the influence of environmental conditions (for specimens kept in an environment with and without temperature and humidity controlled) and age at loading were evaluated. From the obtained experimental results, a comparison was made to the values obtained from the ACI, EC2, NBR, B3 and GL prediction models. The deformability of SCC was analyzed by monitoring a post-tensioned beam prototype followed by the comparison of the measured deflection and strain long the time to those obtained from a finite element model. From the obtained experimental results of creep and shrinkage, the most adequate prediction models are the ACI and GL models. The use of the ACI model with the finite element method produced good results when compared to the experimental measurements of deflection and strain of the prototype beam. With respect to the compliance creep function, it can be noticed that the model provided by the Brazilian Code is adequate to the studied SCC.
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Torres, Fernando Montenegro. "Análise teórico-experimental de consolos de concreto armado." Universidade de São Paulo, 1998. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-26022018-133153/.
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Este trabalho tem o objetivo de analisar teórica e experimentalmente o comportamento de consolos de concreto armado. Para tal, foi realizada uma revisão bibliográfica, buscando os artigos mais recentes e as principais normas que tratam deste assunto. Foram analisados mais de trezentos consolos encontrados na literatura. Nesta análise, as forças de ruína experimentais foram comparadas com a forças de ruínas calculadas segundo as normas: ACI-318M-89, CAN3-A23.3-M-84 e NBR-9062/85. Para complementar este estudo, foram ensaiados oito consolos de concreto de alta resistência, os quais apresentavam: as mesmas dimensões, a mesma armadura principal e diferentes taxas de armadura de costura. A resistência do concreto variou de 50 MPa a 80 MPa. Estes consolos tiveram suas forças de ruína comparadas com as previstas pelas normas já citadas. Além disto, foram analisadas: as deformações na armadura, medidas a cada nível de carregamento, e o ângulo de inclinação das tensões principais, medidos no centro geométrico da provável biela comprimida. De acordo com as análises realizadas, pode-se observar que o uso de concreto de alto desempenho na confecção de consolos é bastante eficaz. Entretanto, é necessário o uso de taxas adequadas de armadura, que são basicamente as mesmas indicadas para consolos de concreto de resistência convencional. O dimensionamento de consolos segundo as normas citadas foi bastante satisfatório. Entretanto, no cálculo da força de ruína das peças ensaiadas por outros pesquisadores, os resultados não foram tão satisfatórios, pois estes consolos analisados nem sempre apresentavam o detalhamento conforme recomendam estas normas.The aim of this work is to analyze theoretically and experimentally the behavior of reinforced concrete corbels. A bibliographic review was done, searching for the most recent papers and the main codes concerning to this subject. It was analyzed more than there hundred corbels found in the literature. In this analysis, the experimental failures forces were compared to the failure forces calculated by the followings codes: ACI-318M-89; CAN3-A23.3-M-84 and NBR-9062/85. To complement this work, eight corbels of high-strength concrete were made with the same dimensions, the same main reinforcement and different rates of secondary reinforcement. The strength of the concrete ranged from 50 MPa to 80 MPa. These corbels had their failure forces compared with the failure forces postulated by the codes. It was also evaluated the deformations of the reinforcement, considered in each level of loading, and the angle of inclination of the main stresses, measured in the geometric center of probable compressed diagonal. By this analysis, it was observed that the use of high-strength concrete in the construction of corbels is quitely efficient. Although, it is necessary the use of proper reinforcement ratios, that are basically the same indicated for corbels with low-strength concrete. The design of corbels by the cited codes was quitely satisfactory. By the way, the calculation of the failure force of corbels made by others researchers were not satisfactory. The probable reason was that the corbels did not present the reinforcement details recomended by these codes.
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Guillermo, La Torre Aldo de Jesus, and Tupac Yupanqui Sergio Silva. "Evaluación y diseño de dos propuestas de reforzamiento para vigas y columnas de concreto armado en una edificación de hotel." Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2019. http://hdl.handle.net/10757/628230.
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La presente investigación radica en la evaluación técnico-económica de dos tipos de reforzamiento estructurales, tales como el polímero reforzado con fibra de carbono (CFRP) y el encamisado de concreto reforzado en los elementos estructurales de vigas y columnas. Esto con el objetivo de determinar la alternativa de solución óptima, teniendo en cuenta que la opción de encamisado de concreto reforzado es comúnmente la más empleada en el sector. En cuanto al proyecto, este corresponde a un edificio de hotel en el cual se requiere hacer cambio de uso en los pisos 3 y 4 incorporando una sala de gimnasio en los pisos ya mencionados. Respecto al diseño de las alternativas de reforzamiento, estas se rigen bajo las exigencias del Reglamento Nacional de Edificaciones del Perú (E020 – Cargas, E030 - Diseño Sismorresistente, E060 – Concreto Armado) y de normas internacionales como la ACI (ACI440.2R – Fibra de carbono, ACI369 - Rehabilitación sísmica de edificios con estructuras de concreto existente, ACI318 – 14 Requisitos de reglamento para concreto estructural). Asimismo, se utilizó el programa Etabs para complementar el análisis del comportamiento estructural de las vigas y columnas. Posterior al diseño, se realizó la evaluación técnico-económica, proponiendo un plan de ejecución (cronograma) acorde con las características y contexto del proyecto, y un presupuesto económico para cada caso. Finalmente, mediante un análisis comparativo que contrasta ambos criterios, se concluye la alternativa de reforzamiento óptima para la edificación de hotel analizada es el CFRP.The present investigation lies in the technical-economic evaluation of two types of structural reinforcement, such as the carbon fiber reinforced polymer (CFRP) and the reinforced concrete jacketing in the structural elements: beams and columns. The objective is to determine the optimal solution alternative, taking into account that the option of reinforced concrete cladding is commonly the most used in the sector. As for the project, it corresponds to a hotel building in which change of use is required on floors 3 and 4 incorporating a gymnasium in the aforementioned floors. Regarding the design of reinforcement alternatives, these ruled by the requirements of the National Building Regulations of Peru (E020 – Loads, E030 – Seismic Resistant Design, E060 – Reinforced Concrete) and international standards such as the ACI (ACI 440 – FRP, ACI 369 – Seismic Rehabilitation of Existing Concrete Frame Builidings, ACI 318 - Requirements for Structural Concrete). Likewise, the program was used to complement the analysis of the structural behavior of the buildings and the reinforcement alternatives. After the design, the technical-economic evaluation was carried out, proposing an execution plan (schedule) according to the characteristics and context of the project, and an economic budget for each case. Finally, by means of a comparative analysis that contrasts both criteria, the optimal reinforcement alternative for the hotel building analyzed is concluded is the CFRP.
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Marchioni, Mariana Lobo. "Desenvolvimento de técnicas para caracterização de concreto seco utilizado na fabricação de peças de concreto para pavimentação intertravada." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/3/3146/tde-18072013-150832/.
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O concreto seco, também chamado de concreto sem abatimento (no-slump) é utilizado na produção de artefatos de cimento, como por exemplo em peças de concreto para pavimentação, blocos para alvenaria e tubos de concreto e ainda como camada de subbase de pavimentos com a técnica de concreto compactado a rolo. A técnica de conformar concretos com reduzido teor de umidade através de equipamentos que aplicam simultaneamente compressão e vibração é amplamente utilizada na produção de artefatos de concreto, como as peças de concreto para pavimentação intertravada. Para as peças de concreto o desafio é ainda maior, pois as especificações de resistência característica à compressão podem chegar a 50 MPa. A principal característica do concreto seco é o baixo teor de água e elevada coesão, necessitando de energia de compactação e vibração para a eliminação de vazios e o concreto assumir a forma desejada. Esta técnica permite a desfôrma imediata, que garante elevada produtividade e consequente diminuição dos custos de produção. Já a compactação permite obter componentes de concreto com menor consumo de cimento se comparados ao concreto plástico. Diferentemente de toda literatura e metodologias de dosagem encontradas para o concreto plástico, o concreto seco encontra barreiras técnicas para a aplicação de metodologias que otimizem sua dosagem, em formulações empíricas que não levam em conta de forma adequada as características dos agregados, características estas diretamente ligadas à compacidade das peças, que por sua vez tem grande influência nas características do produto final. Além disto, há poucos estudos do comportamento reológico do concreto seco, que influenciam a fluidez e coesão da do concreto e que irão determinar a produtividade e qualidade da produção. Dessa forma, neste trabalho é apresentado uma metodologia para caracterização do concreto seco nos estados fresco e endurecido que permite o desenvolvimento sistemático de formulações com maior facilidade de compactação e que também resulte na melhoria do desempenho das peças e diminuindo a necessidade de testes em escala real. O método se baseia em produzir em laboratório um corpo de prova que reproduz as condições de moldagem de uma vibroprensa, eliminando-se a variável da vibração e padronizando as condições de compressão. Nos corpos-de-prova são avaliadas características nos estados fresco e endurecido, além de aspectos do comportamento reológico do concreto, através de técnicas de reologia compressiva. Para aferir a metodologia foram utilizadas amostras de referência produzidas em uma fábrica de peças de concreto. Com a metodologia proposta, foi possível atingir 90% da resistência mecânica das peças produzidas em uma vibroprensa de alta compactação. Sendo assim esta metodologia poderá ser utilizada em estudos de dosagem de concreto seco, portanto o trabalho desenvolvido é indicado na utilização de dosagens de concreto seco, obtendo-se maior ecoeficiência, a medida que otimiza o consumo de cimento da mistura e facilita o estudo de dosagem de materiais alternativos em substituição aos agregados convencionais.The dry concrete, also known as earth moist concrete or no-slump concrete, is most used to manufacture precast concrete products, as paving blocks, masonry blocks and concrete tubes, and also in rolled compacted concrete pavement. Its most important property is the low water content, and it requires mechanical equipment for its compactation. Paving blocks are normally manufactured using vibrocompression equipment, which at the same time applies both compaction and vibration resulting in paving blocks with high durability and mechanical resistance. Even though this technique is highly used it still lacks studies on some important steps of the manufacturing process. The mix design techniques are mostly empirical and dont deeply consider the aggregate characteristics, that are connected with its compacity and, by that, the characteristics of the paving block. Also, there are only a few studies of the rheology characteristics of dry concrete, which relates with de manufacturing process and the easiness that the mix is compacted. So, the object of this study is to develop a dry concrete characterization methodology that allows the systematic development of mix designs that are easily compacted and also improves the performance of the paving blocks.
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Souza, Andréa Resende. "Retração em concreto autoadensável: contribuição de produtos mitigadores." Universidade Tecnológica Federal do Paraná, 2016. http://repositorio.utfpr.edu.br/jspui/handle/1/2330.
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CAPESO concreto autoadensável (CAA) apresenta-se como o concreto do futuro por aumentar o rendimento e reduzir barulho e risco de acidentes nas obras, além de possibilitar a execução de elementos esbeltos ou com elevada taxa de armadura, além da eliminação do processo de adensamento do concreto. No entanto, por apresentar um alto teor de pasta cimento, e refinamento da rede porosa existe o aumento das forças capilares e, por consequência, elevação das mudanças volumétricas presentes na matriz cimentícias, oriundas do processo de retração por hidratação e de secagem dessa matriz. Desta forma, esse trabalho busca avaliar a eficácia de diferentes soluções mitigadoras de retração (autógena e por secagem), em misturas de CAA, sendo utilizado como adições ao estudo: aditivo redutor de retração (SRA), adição compensadora de retração do tipo-S (CSA), fibra polimérica de polipropileno (FP) e um tipo de polímero superabsorvente a base de poliacrilato de potássio (SAP). Com o objetivo de analisar o desempenho dessas adições foram realizados os ensaios de retração, conforme NM 131 (1997) e avaliação da influência dessas adições nas propriedades no estado fresco e endurecido do CAA. As misturas de CAA foram confeccionadas com três diferentes cimentos (CP V ARI, CP II-Z e CP II-E) em combinação com três teores de SRA (1%, 1,5% e 2%), com três teores de CSA (3%, 5% e 7%), com três teores de FP (0,05%, 0,10% e 0,15%) e com três teores de SPA (0,10%, 0,15% e 0,20%) totalizando 39 amostras. Os resultados de ANOVA mostraram que tanto o tipo de cimento, quanto o tipo da adição influenciam significativamente as propriedades avaliadas nesse estudo, tanto as do estado fresco quanto endurecido. Para mitigar a retração autógena e hidráulica foi verificado a influência do tipo de cimento e adição, onde o emprego de CP II-Z reduz a retração entre os cimentos para as misturas de controle, e a adição de 7% de CSA resultam em menores retrações para todos os concretos. Com os resultados obtidos foi verificado que definir o melhor tipo de adição mitigadora da retração ao CAA é um processo complexo, pois exige, além da análise em laboratório, análise da sua aplicação em campo. Ressalta-se que as adições são, em diferentes proporções, capazes de afetar em diferentes ruas, a retração e as propriedades mecânicas do concreto. Deve-se também ressaltar, que tanto a habilidade passante, quanto a perda de trabalhabilidade, são também afetadas pela escolha do tipo de cimento, tipo de adição e teor empregado. Entretanto, em que pese o fato da ocorrência dessas mudanças, foi possível constatar que os concretos produzidos com cimento CP V ARI e fibra polimérica, nos teores de 0,05%, ou com aditivo compensador de retração, no teor de 7%, apresentam-se como potencialmente aplicáveis em várias utilizações.
Self-compacting concrete (CAA) is the concrete of the future for increasing the performance and reducing noise and risk of accidents in the works, besides allowing the execution of slender elements or with a high rate of reinforcement, besides the elimination of the densification process The concrete. However, due to the high content of cement paste and the porous network refinement, there is an increase in the capillary forces and, consequently, increase of the volumetric changes present in the cement matrix, resulting from the retraction process by hydration and drying of the matrix. In this way, this work seeks to evaluate the effectiveness of different retraction mitigation solutions (autogenous and by drying), in CAA mixtures, being used as additions to the study: additive retraction reducer (SRA), compensatory addition of Stype retraction (CSA), polypropylene polymer fiber (FP) and a type of superabsorbent polymer based on potassium polyacrylate (SAP). To analyze the performance of these additions, the retraction tests were performed according to NM 131 (1997) and evaluation of the influence of these additions on the fresh and hardened CAA properties. The CAA mixtures were made with three different cements (CP V ARI, CP II-Z and CP II-E) in combination with three contents of RAS (1%, 1,5% and 2%), with three levels of CSA (3%, 5% and 7%), with three levels of PF (0.05%, 0.10% and 0.15%) and three SPA contents (0.10%, 0.15% and 0.20%) totaling 39 samples. The results of ANOVA showed that both the type of cement and the type of addition significantly influence the properties evaluated in this study, both fresh and hardened. In order to mitigate the autogenous and hydraulic retraction, the influence of cement type and addition was verified, where the use of CP II-Z reduces the retraction between the cements for the control mixtures, and the addition of 7% of CSA results in smaller retractions For all concrete. With the results obtained, it was verified that defining the best type of addition mitigation of retraction to the CAA is a complex process, since it requires, besides the analysis in the laboratory, analysis of its application in the field. It should be noted that the additions are, in different proportions, able to affect in different streets, the retraction and the mechanical properties of the concrete. It should also be noted that both the throughput and the loss of workability are also affected by the choice of cement type, type of addition and content employed. However, in spite of the fact of the occurrence of these changes, it was possible to verify that the concretes produced with cement CP V ARI and polymer fiber, in the contents of 0.05%, or with compensating additive of retraction, in the content of 7%, present Themselves as potentially applicable in various uses.
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Silva, Patricia Ribeiro da. "Influência de adições minerais e aditivo impermeabilizante interno no desempenho de telhas protendidas pré-fabricadas em concreto." Universidade Tecnológica Federal do Paraná, 2011. http://repositorio.utfpr.edu.br/jspui/handle/1/317.
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Com o surgimento da tecnologia da pré-fabricação, a construção civil tem adquirido elevada agilidade, reduzindo os prazos de construção e maior qualidade no controle de execução. Dentre as diversas peças pré-fabricadas, a telha em concreto protendido autoportante tem por característica cobrir vãos de até 25 m, sem a existência de estrutura de apoio intermediária. Sendo um produto esbelto, exige um aprimoramento constante para aumentar a durabilidade da estrutura quanto à corrosão da armadura e manter sua adequação ao uso. O objetivo desse trabalho é reduzir a permeabilidade das telhas pré-fabricadas, além de analisar a influência desse parâmetro na durabilidade do concreto frente às classes de agressividade da norma NBR 9062/2006. A norma estabelece um fator a/c máximo de 0,45 e resistência característica à compressão mínima de 40 MPa, enquadrando-se como classe de agressividade ambiental II - Urbana. Para tal, foram escolhidas algumas adições minerais existentes na região da grande Curitiba (metacaulim e filler), além de um aditivo impermeabilizante interno, comparando com o traço de referência preexistente em linha de produção. As dosagens foram definidas com base no empacotamento de partículas e caracterizadas quanto à resistência mecânica à compressão, absorção de água por imersão e por capilaridade e, penetração de água sob pressão, além dos ensaios de porosimetria por intrusão de mercúrio (PIM), carbonatação e penetração de íons cloreto. Em termos de resistência mecânica à compressão, a dosagem referência apresentou os melhores resultados (em função da menor relação água/cimento e maior consumo de cimento), seguido pelo concreto com aditivo impermeabilizante e com metacaulim. Para a absorção de água, todas as dosagens apresentaram-se como concretos duráveis, com destaque para o metacaulim e filler+aditivo impermeabilizante. Quanto à absorção capilar, todas as dosagens apresentaram baixa permeabilidade. Para a penetração de água sob pressão todas se apresentam como impermeáveis em condições agressivas, com destaque para o uso do metacaulim e do aditivo impermeabilizante. O ensaio de PIM mostra que a dosagem com filler possui uma concentração maior de poros e que a dosagem com metacaulim apresenta o menor diâmetro máximo de poros, com uma tendência ao refinamento em diâmetros menores. Quando analisado o resultado de carbonatação, o metacaulim apresentou o melhor resultado, possibilitando um menor cobrimento da armadura para uma vida útil de 50 anos. Quanto à penetração de cloretos, a dosagem com metacaulim, apresentou uma redução maior em relação às demais dosagens pela sua atividade pozolânica, contribuindo para a durabilidade do concreto. Em linhas gerais, é possível melhorar a impermeabilidade do concreto com o acréscimo de 8% do metacaulim sobre o peso do cimento, ainda com uma redução de 5,2% de cimento, com bons resultados também para o uso de 1% de aditivo impermeabilizante. Quanto à durabilidade, a otimização da curva granulométrica dos agregados e o uso do metacaulim possibilitam a utilização de telhas pré-fabricadas em regiões de classe de agressividade III - Industrial ou Marinha, observando o cobrimento mínimo da armadura.With the emerging precast concrete technology, the civil construction has acquired high agility, reducing construction time and greater quality control in execution. Among several precast pieces, tile in prestressed concrete is characterized by selfsupporting spans of up to 25 m, without the existence of an intermediate support structure. Being a slim product, requires an improvement in increasing the durability of the structure because of the steel corrosion and maintain their fitness for use. The objective of this research is to reduce the permeability of the precast tiles, and analyzing their influence in the durability of the concrete face of the aggressiveness classes constants in the NBR 9062/2006, that establish the a/c ratio up to 0,45 and minimum compressive strength characteristic of 40 MPa, positioning themselves as a class of environmental aggressiveness II - Urban. For this, were selected a few mineral admixture from Curitiba/Paraná and a waterproof internal admixture, comparing with the concrete mix pre-existing in production line. The concrete dosages were defined by packing particles and were analysed for mechanical compressive strength, water absorption by immersion and by capillarity and water penetration under pressure, in addition to tests of mercury intrusion porosimetry (MIP), carbonation and chloride ion penetration. About the mechanical compressive strength, the dosage reference showed the best results (due to lower water / cement ratio and higher cement consumption), followed by concrete with waterproofing admixture and metakaolin. For water absorption, all measurements fall as durable concrete, especially the metakaolin additive and filler + waterproofing. For the water absorption, all dosages presented low permeability. For the water penetration under pressure all fall as impervious to several conditions, especially with metakaolin and waterproofing admixture. The MIP test shows that the dosage with filler has a higher concentration of pores and the dosage with metakaolin has the smallest maximum diameter of pores, with a tendency towards refinement in smaller diameters. When analyzing the carbonation, the metakaolin showed the best results, allowing a smaller reinforcement cover for a lifetime of 50 years. As the penetration of chlorides ions, the metakaolin, showed a greater reduction comparing with other dosages for its pozzolanic activity, contributing to the concrete durability. In general, it is possible to improve the concrete impermeability with the addition of 8% of metakaolin by weight of cement, with 5,2% of cement reduction, showing good results also using 1% of waterproofing admixture. As for durability, the optimizing of aggregates granulometric curve and the use of metakaolin enables the use of prefabricated tiles in regions of class of environmental aggressiveness III - Industrial or Marine, observing the minimum concrete cover of reinforcement.
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Bayer, Raci Ismail. "Use Of Preplaced Aggregate Concrete For Mass Concrete Applications." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/3/12605131/index.pdf.
Full textAbstract:
Heat of hydration is a source of problem in mass concrete since it causes the difference between the inner and the outer temperatures increase excessively, which leads thermal cracks. The first step in fighting against this problem is to keep the initial temperature of concrete as low as possible. From this point of view, Preplaced Aggregate Concrete (in short PAC) is quite advantageous, because the friction taking place among the coarse aggregates during the mixing operation causes the initial temperature of concrete increase. However, since coarse aggregates are not subjected to the mixing operation in PAC method, comparatively lower initial temperatures can be achieved. On the other hand, making PAC by the conventional injection method is quite troublesome, since it requires special equipment and experienced workmanship. Because of this, it would be very useful to investigate alternative methods for making PAC.
In this research, a new method for making PAC has been investigated. The new method is briefly based on increasing the fluidity of the grout by new generation superplasticizers to such an extent that, it fills all the voids in the preplaced coarse aggregate mass when it is poured over, without requiring any injection. In the scope of the study, twelve concrete cube specimens, each with 1 m volume, have been preparedone of which as conventional concrete, seven of which as PAC by injection method, and four of which as PAC by the new method mentioned above. In order to examine the specimens that have been prepared by three different methods from thermal properties point of view, the difference between the central and the surface temperatures of the specimens have been followed by the thermocouples located in the specimens during preparation. Also, in order to examine the mechanical properties of the specimens, three core specimens have been taken from each specimen at certain ages, compressive strength and modulus of elasticity tests have been carried out on these core specimens. As a result of the experiments it has been observed that, the PAC specimens prepared by injection method performed better from thermal properties point of view, but worse from mechanical properties point of view than conventional concrete. On the other hand, the PAC specimens prepared by the new method have performed both as well as the other PAC specimens from thermal properties point of view, and as well as conventional concrete from mechanical properties point of view.
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Selander, Anders. "Hydrophobic Impregnation of Concrete Structures : Effects on Concrete Properties." Doctoral thesis, KTH, Brobyggnad inkl stålbyggnad, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12179.
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Hydrophobic impregnations often referred to as water repellent agents, today mainly consisting of alkylalkoxysilanes, are often used on concrete to prolong the service life of the structure. This is accomplished by protecting the reinforcement bars from chlorides or by changing the moisture content inside. When the concrete is treated with a water repellent agent the properties of the surface layer becomes hydrophobic and thereby water droplets are stopped from entering, still allowing water vapour to pass through. This change can reduce chloride ingress and stop heavy rain from penetrating through the surface layer. This thesis presents results concerning how the properties of concrete are affected by a hydrophobic impregnation. Moisture transport and fixation in the surface layer of the concrete are studied as well as the secondary effects of more practical use such as the effect on chloride ingress, water absorption and humidity level. It also presents results on how the penetration depth and concentration of the water repellent agent (i) depend on a number of parameters, and (ii) affect the outcome of the treatment. Water repellent treatments on a number of different concrete structures in Stockholm, ranging from tunnel to high-rice building, are evaluated as well. The three most important factors for the penetration of any water repellent agent into concrete are time, porosity and degree of saturation. A semi-empirical equation is derived that gives an idea on how much these factors affect the efficient penetration depth of the water repellent agent. The depth and concentration have a major effect on the performance of the treatment. The moisture diffusion coefficient for a water repellent treated concrete is close to constant and not nearly as dependent on the relative humidity (RH) as for untreated concrete. Unlike untreated concrete, where capillary suction plays an important role for the moisture transport at high RH, the vapour transport is the dominant transport mechanism even at high RH for water repellent treated concrete. The moisture fixation is affected by a water repellent treatment and the effect is clearest at high moisture levels. The main reason for this is that the capillary porosity is affected by the treatment to a relatively high degree while the gel porosity to a large extent remains unaffected. A hypothesis is presented which suggests that the RH inside the concrete at the time of the treatment affects not only the depth and concentration but also in which range of pore radii the water repellent agent is present and active. The durability of hydrophobic impregnations can be divided into surface effects and in depth effects. The first is sensitive to the environmental and mechanical loadings and normally disappears within a year while the later can be long lasting if a sufficient depth is reached. Hydrophobic impregnations are not the answer to all problems in concrete related to moisture, but if correctly used it can prolong the service life of the structure which will lead to savings of natural resources and thus both economical and environmental savings for the community.Vattenavvisande impregneringsmedel, som i dagsläget till största del består av alkylalkoxysilaner, används ofta på betong för att förlänga livslängden på konstruktionen. Detta syfte uppnås genom att armeringen skyddas mot klorider eller att fukthalten inuti betongen sänks. När betongen impregneras ändras ytskiktets fuktmekaniska egenskaper från hydrofila till hydrofoba vilket gör att vattendroppar kan stoppas medan vattenånga tillåts passera. Dessa förändrade egenskaper kan medföra att kloridinträngningen minskar och att kraftiga regn inte tränger genom det impregnerade skiktet. Denna avhandling presenterar resultat om hur betongen påverkas av en vattenavvisande impregnering. Fukttransport och fuktfixering i betongens ytskikt har undersökts men även sekundära effekter som kloridinträngning, vattenabsorption och förändring i fuktinnehåll vilka alla är av större praktisk nytta. Avhandlingen presenterar också resultat om vilka faktorer som påverkar impregneringens inträngningsdjup och koncentration samt vilken betydelse dessa har för funktionen. För att utvärdera impregneringars effekt i olika miljöer har ett stort antal objekt i Stockholm undersökts, innefattande olika konstruktioner från en tunnel till höghus. Impregneringens inträngningsdjup och koncentration har en avgörande betydelse för dess funktion. De tre viktigaste faktorerna för alla impregneringsmedels inträngning i betong är tid, porositet och fuktnivå. En semiempirisk ekvation har tagits fram där det framgår hur dessa tre faktorer påverkar det slutliga inträngningsdjupet för impregneringen. Till skillnad från obehandlad betong är transportkoefficienten för en impregnerad betong nästan oberoende av den relativa fuktigheten (RF) i omgivningen. Vid höga RF, där största delen av fukttransporten i obehandlad betong sker på grund av kapillärkrafter, är ångtransporten fortfarande den dominerande transportmekanismen i impregnerad betong. Fuktfixeringen i betong påverkas av en impregnering och effekten är störst vid höga RF. Det är dock tydligt att en viss mängd fukt finns inuti den impregnerade betongen. Detta kan förklaras med att största delen av kapillärporerna påverkas av impregneringen medan gelporerna förblir obehandlade. Resultaten indikerar också att fuktnivån vid impregneringstillfället avgör vilken del av porsystemet som kan behandlas och inte bara koncentrationen och inträngningsdjupet. Långtidsegenskaperna hos impregneringen kan delas upp i yt- och djupeffekt. Effekten på ytan avtar normalt sett inom ett år på grund av damm och partiklar, UV-ljus, slitage mm. Djupeffekten påverkas däremot inte av dessa faktorer och kan finnas kvar i decennier. Vattenavvisande impregneringar är inte lösningen på alla fuktrelaterade problem i betong, men om de används på rätt sätt så kan det förlänga livslängden på många konstruktioner. Detta leder till ett bättre hushållande med naturresurser och därmed både ekonomiska och miljömässiga besparingar för samhället.
QC20100715
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Svecová, Dagmar. "Behaviour of concrete beams reinforced withFRP prestressed concrete prisms." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0006/NQ42809.pdf.
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Baali, Lama. "Self-consolidating concrete for precast, prestressed concrete bridge elements." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40689.
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The following thesis presents the results of four full scale beams tests as part of a research program conducted at McGill University. The purpose is to study the applicability of existing design provisions, in the American Association of State Highway and Transportation Officials (AASHTO) specifications, for the use of self-consolidating concrete (SCC) in precast pretensioned bridge girders. The test specimens had an overall length of 31 ft (9.4m) with a center-to-center span of 29 ft (8.8m). They were cast in four batches with different concrete attributes: two non air-entrained SCC mixtures and two high-performance concretes. For each type, compressive strengths of 8,000 and 10,000 psi (55.2 and 69 MPa) with release strengths of 5,000 and 6,250 psi (34.5 and 43 MPa) at 18 hours, respectively, were tested. Each girder was prestressed with eight Grade 270 seven-wire low-relaxation prestressing strands of 0.6 in (15.2 mm) diameter. Six of the strands were straight and two were harped twice, 4’-11” (1.5 m) from mid-span. The specimens were supported on neoprene bearing pads at their ends, and were tested with two equal point loads located 4’-11” (1.5 m) from mid-span. This research project demonstrated that the shear failure of the girders exceeded the predicted nominal shear resistance given by the 2004 AASHTO Specifications. The experimental flexural resistance also exceeded the predicted nominal resistance.Le présent mémoire expose les résultats de quatre poutres pleine grandeur faisant partie intégrante d’une étude effectuée à l’Université McGill. Le but de cette étude est de valider l’applicabilité des provisions de conception existantes, de l’Association Américaine des Autoroutes d’État et des Officiers de Transport (norme AASHTO), pour l’usage de béton autoplaçant (BAP) dans les poutres précontraintes et préfabriquées de ponts.Les spécimens testés ont une longueur maximale de 31 pieds (9.4 m) avec une distance du centre au centre de 29 pieds (8.8 m). Les poutres ont été coulées une à la fois avec différentes sortes de béton: deux d’entres-elles à partir de béton autoplaçant sans air entrappé, et deux avec du béton haute-performance. Pour chaque sorte, une résistance compressive de 8,000 et 10,000 psi (55.2 et 69 MPa) avec une résistance, avant de précontraindre le béton, de 5,000 et 6,250 psi (34.5 et 43 MPa) à 18 heures, respectivement, ont été testées. Chaque poutre était précontrainte avec huit tendons, grade 270, de 0.6 in (15.2 mm) de diamètre. Six de ces tendons étaient horizontaux alors que deux étaient inclinés 59 pouces (1.5 m) de chaque bord de l’axe central. Les spécimens étaient supportés aux deux extrémités sur des pads de néoprène et étaient testés avec deux charges concentriques situées 59 pouces (1.5 m) de l’axe central.Cette recherche à démontrer que la capacité en cisaillement des poutres testées excédait les valeurs nominales prévues par les normes AASHTO 2004. Les valeurs expérimentales de la résistance à la flexion des poutres aussi excèdent les valeurs nominales prédises.
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Saad, Ahmad. "Material properties of concrete used in skewed concrete bridges." Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-54412.
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This thesis has discussed both properties and geometry of concrete slabs used in bridges. It gave understanding on behavior of concrete in both tension and compression zones and how crack propagates in specimens by presenting both theory of fracture and performing concrete tests like tension splitting, uniaxial compression and uniaxial tension tests. Furthermore, it supported experimental tests with finite elements modelling for each test, and illustrated both boundary conditions and loads. The thesis has used ARAMIS cameras to observe crack propagations in all experimental tests, and its first study at LNU that emphasized on Brazilian test, because of importance of this test to describe both crushing and cracking behavior of concrete under loading. It’s an excellent opportunity to understand how concrete and steel behave individually and in combination with each other, and to understand fracture process zone, and this has been discussed in theory chapter. The geometry change that could affect stresses distributions has also described in literature and modelled to give good idea on how to model slabs in different angles in the methodology chapter. Thus, thesis will use finite elements program (Abaqus) to model both experimental specimens and concrete slabs without reinforcement to emphasize on concrete behavior and skewness effect. This means studying both properties of concrete and geometry of concrete slabs. This thesis has expanded experimental tests and chose bridges as an application.
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Döse, Magnus. "Ionizing Radiation in Concrete and Concrete Buildings : Empirical Assessments." Licentiate thesis, KTH, Betongbyggnad, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-192956.
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One of the major issues with radiation from the natural isotopes 40K, 226Ra (238U) and 232Th and their decay products is the forthcoming legislation from the European Commission in relation to its Basic Safety Directive (2014). The European legislation is mandatory and could not be overthrown by national legislation. Hence, even though the BSS is still a directive it is foreseen as becoming a regulation in due time. The reference value of the natural isotopes, from a radiation point of view, set for building materials is 1 mSv per year (EC, 2014). Earlier recommendations (The Radiation Protection Authorities in Denmark, Finland, Iceland, Norway and Sweden, 2000) within the Nordic countries set an upper limit at 2 mSv per year of radiation from building materials. The main objective within the frame of the thesis was to investigate gamma radiation in relation to Swedish aggregates and their use as final construction products and the applicability and use of a model (EC, 1999) for building materials to calculate the effective dose within a pre-defined room. Part of the thesis also investigates different methodologies that can be used to assess the radiation in a construction material made up of several constituents (building materials) and aims to show that for some purposes as for the construction industries (precast concrete), that a hand-held spectrometer can be used with good accuracy, even though the object is limited in thickness and size. Secondly, the author proposes a simplified way of assessing the radiation in a construction material by use of correlation coefficient of a specified recipe by use of a hand-held spectrometer. Moreover, an understanding of the different building materials´ contribution to the finalized construction product, e.g. concrete is demonstrated, and how to achieve a good control of the radiation levels in the concrete building.QC 20160926
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Dodds, Wayne J. "Durability performance of coarse crushed concrete aggregate structural concrete." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/27534.
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Crushed or recycled concrete aggregates (CCA/RCA) is an increasingly popular material as a replacement for natural aggregates in concrete due to industry demands for more recycled, lower carbon and responsibly sourced materials. In the UK, the majority of CCA is utilised in non-structural applications such as: a general fill material, road base/subbase or in low-grade concrete. Recycled aggregate producers however, are seeking new ways to incorporate CCA into higher value applications such as structural concrete to increase profits. Opportunities to incorporate CCA into structural concrete may also arise because of project demands for sustainability or in situations where natural aggregates are in short supply. Limited research has been published regarding the effect of coarse CCA on the durability of structural concrete, particularly in respect to water and chloride ion ingress and possibility of corrosion initiation. The aim of this EngD research programme was to investigate the effect of coarse CCA and supplementary cementitious materials (SCMs) on the durability performance of structural concrete, with particular emphasis on the key liquid transport mechanisms within concrete, namely absorption by capillary action, diffusion and migration. This addressed an industry concern regarding the detrimental effect of coarse CCA which has resulted in a limit on replacement levels of coarse natural aggregates in structural concrete, as defined in Eurocodes and local national standards for concrete. In this study, structural concrete was produced with varying levels of coarse CCA replacement (up to 100%), from five different sources and/or structural elements across the UK, with various combinations of SCMs to replace in part the Portland cement. Petrographic analysis was used as an innovative technique to characterise the coarse CCA sources to determine suitability which yielded positive results. The durability performance of the resultant concrete was analysed by exposing the concrete to aggressive chloride environments. The results indicate that the inclusion of coarse CCA, even as low as 20%, had a detrimental effect on the durability performance of structural concrete, in relation to absorption by capillary action, diffusion and migration. This effect however, can be offset through the use of SCMs, which have been shown to outperform control Portland cement concrete with 100% natural aggregates in durability performance tests. The results also suggest that cementitious materials had a greater influence on durability performance than the type and source of coarse aggregates used. It is recommended that the replacement of natural aggregate with coarse CCA be limited to 30% in cases where compliance with the 28 day characteristic strength is of particular importance. If the criterion for compliance at 28 days can be relaxed and the compressive cube strength of concretes with SCMs tested at later ages for conformity (56 or 90 days), then higher quantities of coarse CCA may be incorporated up to 60% to produce a more sustainable structural concrete. It is recommended that Portland cement is partially replaced with 50% ground granulated blast-furnace slag (GGBS) to produce a CEM III/A concrete. This is a significant step towards the potential wider implementation of coarse CCA in structural concrete, provided a suitable quantity of SCM is adopted along with a reliable and consistent source of coarse CCA.
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Habouh, Mohamed I. "SHEAR TRANSFER STRENGTH OF CONCRETE PLACED AGAINST HARDENED CONCRETE." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1439564977.
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Sibanda, Bongani. "Vibration based performance assessment of concrete-concrete composite bridges." Master's thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/8988.
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Includes bibliographical references (leaves 142-148).Concrete composites consisting of precast pre-stressed standardized beams and a cast in-situ deck slab have been used for the construction of short to medium span bridges for the past four decades in South Africa and worldwide. The pre-cast beams and cast in-situ slab are commonly connected using shear connectors. Failure of these connectors would compromise the composite action of the structure, thus reducing the load carrying capacity and hence its efficiency. This study seeks to assess the integrity of such shear connectors using dynamic testing and Finite Element (FE) analysis. The main objective of the work is to assess the practicality of vibration-based techniques to detect damaged shear connectors using experimental and analytical modal data. A scaled bridge model was constructed and 10 mm bolts connected the beams and slab to simulate shear connectors in the prototype bridge. Different damage scenarios were introduced by loosening some of the connectors and vibration testing was done to detect the artificial damage. An FE model of the system was also developed. The shear connectors were modelled as non-linear spring elements capable of simulating the composite action between the slab and beams. Damage of shear connectors was simulated by reducing the spring stiffness. The updating of the FE model was done manually by adjusting appropriate spring stiffnesses. The experimental and analytical results show that the natural frequencies are sensitive to this damage. The frequencies dropped from undamaged to severe damaged structure. Very little information was deduced from the damping ratios, modal assurance criteria (MAC) and coordinate modal assurance criteria (COMAC) values. The experimental and analytical first bending, torsion and transverse modes were sensitive to the damaged shear connectors. 65% of damaged connectors were located using these modes. Using experimental modal data, the mode curvatures and flexibility changes were able to locate the damaged region when more than 35% of shear connectors were loosened. However, using numerical data, the mode curvatures and flexibility changes were able to localize the damaged region for 6% damage introduced. 75% of the loosened connectors were identified. The stiffness change technique could only identify less than 10% of damaged shear connectors using experimental modal data. The same technique was applied on analytical data and over 75% of damaged shear connectors were located. The FE modelling of shear connectors used in this work was applied on an existing bridge. Van der Kloof bridge (South Africa) was constructed using precast pre-stressed beams and a cast in-situ slab. Extended beam web stirrups were used as shear connectors. The main aim was to develop a robust FE model for this bridge that could be used in future to investigate the condition of shear connectors. Using 6-0 non-linear spring elements to model the shear connectors, a maximum difference of 0.98% was observed between the measured and theoretical frequencies after manual updating. This is quite a small difference. This model could therefore be used as a true representative of the physical structure for future investigations.
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Kamat, Anuja Ganesh. "Split Concrete Model for Shear Behavior of Concrete Beams." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/193611.
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Split Concrete Model (SCM) is a unified approach towards modeling shear behavior in concrete. SCM is essentially a rational model which is evaluated and modified using a large experimental database.The shear strength of the concrete beam is modeled as the sum of the contribution of concrete, transverse reinforcement, longitudinal reinforcement and bond between concrete and longitudinal reinforcement. Concrete does not contribute to the shear strength after the formation of the crack. In SCM, this is shown to be accurately modeled by only considering the second branch of the critical crack while computing the contribution of concrete towards shear strength of the beam. Formation of the second branch of the critical crack and immediate subsequent failure of the beam has been compared to the split-cylinder test, which forms the conceptual basis of SCM.SCM computes the concrete contribution using the split tensile strength and the area under compression of the concrete beam. For cases where a split-cylinder test is not performed, a mathematical model is proposed to compute the split tensile strength using the compressive strength of concrete available from experimental results. This model is proposed using advanced statistical methods, including weighted residuals and Box-Cox transformation and is validated using various statistical procedures. The transverse reinforcement contributes to the shear strength of the concrete beam only after the formation of the crack. In SCM, this is shown to be accurately modeled by only considering the first branch of the critical crack while computing the contribution of the transverse reinforcement towards shear strength of the beam, instead of the conventional approach of considering the entire length of the crack. The contribution of the longitudinal steel and bond between concrete and longitudinal steel and concrete is accurately modeled unlike the conventional approaches which do not consider this contribution.Evaluation using the database shows that SCM can predict accurate results for all ranges of strength, depth, reinforcement ratio, and shear span to depth ratio of the beam. This shows that all the influencing parameters for concrete shear strength have been correctly modeled in SCM. SCM gives more accurate results as compared to current codified approaches as verified with design examples. Finally, specific recommendations have been made indicating how the shear design requirements in the current ACI code can be modified.
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Ferreira, Diego de Vasconcelos Gonçalves. "Edifícios com lajes maciças e paredes portantes pré-moldadas de concreto leve com pérolas de EPS." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-29072013-114842/.
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Atualmente, muitas empresas de construção civil não acompanham o avanço tecnológico, preferindo utilizar sistemas convencionais em vez de investir em novas soluções. Além disso, há sérios problemas com mão de obra, que estão cada vez mais presentes na sociedade. Este trabalho apresenta o projeto de um edifício com elementos pré-moldados de Concreto Leve com pérolas de EPS, considerando lajes prontas maciças e paredes portantes, executadas com esse tipo de material. A princípio, foram considerados os estados limites últimos e de serviço para os elementos da estrutura, utilizando os modelos clássicos de análise estrutural. Para modelagem do edifício, foi utilizado o programa comercial SAP2000. Quanto aos procedimentos para dimensionamento das peças, foram preparadas planilhas do Excel, enquanto o detalhamento foi realizado por meio do AutoCAD. Definido o projeto estrutural, foram considerados aspectos construtivos na fábrica e na obra, levando em conta os custos de produção e de transporte, além de apresentar as vantagens que esse sistema construtivo pode proporcionar. Esses custos foram considerados para as lajes prontas maciças e para as paredes pré-moldadas. Mesmo levando em conta apenas os custos de produção e de transporte, o Concreto Leve com EPS foi comparado com o Concreto Autoadensável, o que permitiu visualizar as vantagens do primeiro, quando for considerado o custo global do empreendimento.Currently, many construction companies do not follow the technological advances, preferring to use conventional systems rather than investing in new solutions. Moreover, there are serious problems with manpower, which are increasingly present in society. This work presents the design of a building with precast elements of lightweight concrete with EPS beads, considering solid slabs ready to use and load bearing walls, made with this type of material. As a rule, the ultimate limit states and serviceability were considered for the elements of the structure, using classical models of structural analysis. For modelling the building, the commercial software SAP2000 was used. Regarding the procedures for dimensioning of the pieces, Excel spreadsheets were prepared, while the detailing was carried out by means of the AutoCAD. Defined structural design, construction aspects were considered in the factory and in the work, taking into account costs of production and transportation, besides presenting the advantages that this constructive system can provide. These costs were considered for the solid slabs ready to use and for the precast walls. Even taking into account only the cost of production and transportation, the Lightweight Concrete with EPS was compared with Self-compacting Concrete, allowing visualize the advantages of the former when considering the overall cost of the project.
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Bazalar, La Puerta Luis Ricardo, and Calderón Miguel Antonio Jesús Cadenillas. "Propuesta de agregado reciclado para la elaboración de concreto estructural con f’c=280 kg/cm2 en estructuras aporticadas en la ciudad de Lima para reducir la contaminación ambiental." Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2019. http://hdl.handle.net/10757/628103.
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El presente trabajo de investigación para optar el título en Ingeniería Civil, con énfasis en la rama de construcción, tuvo como finalidad evaluar y comparar el comportamiento del concreto con diferentes proporciones de sustitución de agregado grueso natural (AN) por agregados de concreto reciclado (ACR) con el fin obtener un diseño de concreto que permita la disminucion y uso de agregados naturales, y asi disminuir la depredacion de canteras. El comportamiento se evaluó mediante el análisis de las propiedades mecánicas y durabilidad de los tipos de mezclas realizados con el objetivo de obtener una proporción de sustitución óptima de AN por ACR para que las propiedades se encuentren dentro de los parámetros que indican las normas. Por otro lado, se realizó un modelo de una estructura aporticada para hacer una Evaluación de Impacto Ambiental mediante el uso de la metodología Life Cycle Assessment (LCA) en el programa Athena y, posteriormente, se comparó los resultados obtenidos en dicho programa.The present research work to choose the degree in Civil Engineering, with emphasis in the construction branch, had the purpose of evaluating and comparing the behavior of concrete with different proportions of substitution of natural coarse aggregate (AN) by aggregates of recycled concrete (ACR ) in order to obtain a concrete design that allows the reduction and use of natural aggregates, and thus reduce the depredation of quarries. The behavior was evaluated by analyzing the mechanical properties and durability of the types of mixtures made with the objective of obtaining an optimal substitution ratio of AN by ACR so that the properties are within the parameters indicated by the standards. On the other hand, a model of a contributed structure was made to make an Environmental Impact Assessment by using the Life Cycle Assessment (LCA) methodology in the Athena program and, subsequently, the results obtained in said program were compared.
Tesis
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Vogt, Carsten. "Ultrafine particles in concrete : Influence of ultrafine particles on concrete properties and application to concrete mix design." Doctoral thesis, KTH, Betongbyggnad, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12161.
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Zhuang, Jianmin. "Evaluation of concrete mix designs to mitigate early-age shrinkage cracking in bridge decks." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Thesis/Summer2009/j_zhuang_072709.pdf.
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Thesis (M.S. in civil engineering)--Washington State University, August 2009.Title from PDF title page (viewed on Sept. 21, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 93-96).
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Leite, Ana Cecilia Ferreira. "Comportamento estrutural de edificações de concreto de múltiplos pavimentos considerando o efeito construtivo." Universidade Católica de Pernambuco, 2015. http://www.unicap.br/tede//tde_busca/arquivo.php?codArquivo=1175.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorNos últimos anos, a indústria da construção civil experimentou um forte crescimento na demanda por edifícios de múltiplos pavimentos de concreto armado. Este comportamento do mercado impulsionou construtores a acelerar todas as etapas do processo de construção, a fim de entregar a edificação em um tempo cada vez mais curto. Como decorrência deste fato, as estruturas são carregadas mais precocemente, ocasião em que as suas propriedades de resistência e deformação ainda não se encontram suficientemente maduras para suportar o carregamento construtivo que a solicita. Com a finalidade de compreender quais consequências são provocadas por esse carregamento prematuro da estrutura e analisar a importância dos efeitos construtivos no projeto de edificações de concreto armado, o trabalho traz o resultado de análises não-lineares realizadas com o Método dos Elementos Finitos adotando uma abordagem usualmente referida como staged construction construção em estágios aplicada a uma edificação real, situada na Cidade do Recife, Estado de Pernambuco, Brasil. Nestas análises foram levados em consideração os efeitos da retração, fluência e envelhecimento do concreto. Os resultados obtidos demonstram que os deslocamentos verticais nos pilares, decorrentes dos efeitos construtivos, são fortemente alterados quando comparados com os deslocamentos verticais resultantes da análise sem a consideração dos estágios de construção. A não consideração desses efeitos construtivos podem, em alguns casos, conduzir a manifestações patológicas importantes na edificação.
The building industry has experienced in recent years a strong growth in demand in general and in the case of reinforced concrete buildings this increase has been more marked. This fact has also contributed to accelerate all stages of the production process of these constructions with more pronounced effects on the methodologies used in the constructive steps that influence directly the structural design of the building. Structures loaded at ever earlier ages, in which the strength and deformation properties of materials are not yet sufficiently mature, it is a variable that needs to be taken into account already in the design phase so that the concrete structure behaves within acceptable level of reliability taking into account design code recommendations for service life. To understand the importance of constructive effects and to assess its magnitude in the execution of reinforced concrete buildings, this paper present result from nonlinear analyses using Finite Element Method adopting an approach commonly referred as staged construction applied to a typical building found in the practice. The effects of creep and shrinkage were considered and the results obtained demonstrate that the strains due to constructive effects can, in certain cases, assume representative values which, if ignored, can lead to important pathologies in the building.
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Movassaghi, Ramtin. "Durability of Reinforced Concrete Incorporating Recycled Concrete as Aggregate(RCA)." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/2884.
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Abstract, The interest in using recycled construction materials is derived from the growth in construction and demolition waste due to rehabilitation and natural and technological disasters. The driving force for recycling concrete is three-fold: preserving natural resources, utilizing the growing waste and saving energy and money. While some waste concrete is currently being crushed and used for grading and base material for highways, it has not been used as the aggregate in new concrete in Canada, largely because of the plentiful supply of good quality virgin material. However, crushed concrete is being used in new concrete in other parts of the world where the local aggregate is inferior, and there is now a push within the Canadian cement and concrete sector to improve the industry sustainability, one aspect of which is recycling of materials.
The research done to date has emphasized the influence of recycled concrete aggregate (RCA) on the workability and strength of the new concrete with little attention being paid to the behaviour in service. In contrast, the present study is focused on the durability of concrete containing RCA in reinforced structures. Since the most common cause of failure of reinforced concrete structures in this part of the world is corrosion of the reinforcement by de-icing salts, the focus of the project is on this aspect of durability. The project involves a comparative study of the durability of three concrete mixtures containing, as coarse aggregate:
- new clean recycled concrete aggregate (NC-RCA) obtained by crushing the excess concrete returned to the ready mix yard;
- old de-icing salt contaminated, recycled concrete aggregate ( OC-RCA) from a demolished bridge over Highway 401 in Ontario;
- natural aggregate as a control material.
The electrochemical corrosion behaviour of the steel was monitored using linear polarization resistance and cyclic polarization techniques. In addition, the physical properties of the materials were assessed. For the aggregates, water absorption, chloride content and susceptibility to abrasion were determined. For the concretes, compressive strength, salt scaling resistance and chloride permeability were measured and microscopic observation of the interfacial zones between the aggregate and the new cement paste were conducted.
On the basis of the results, it is concluded that the durability and the strength of the RCA concrete is very dependent on the age of the RCA aggregate. Water and chloride permeability, and, salt scaling and reinforcing steel corrosion resistance of concrete made with a very well hardened old RCA were comparable with or better than those of in normal concrete. Concrete incorporating new RCA exhibited inferior properties and consequently, it is recommended that, the OC-RCA concrete can be used as a sustainable material in structural applications.
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Kukla, Konrad K. "Concrete at high temperatures : hygro-thermo-mechanical degradation of concrete." Thesis, University of Glasgow, 2010. http://theses.gla.ac.uk/1666/.
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The main aim of the presented work is the development of a reliable and coherent solution approach to investigate thermo-hygro-mechanical behaviour of concrete, especially under severe heating conditions. The work focuses on the development and extension of an existing analytical, numerical and constitutive model developed at the University of Glasgow. This is then used as a predictive modelling tool to investigate the response of concrete structures subject to combined thermo-mechanical loads. The thesis focuses initially on the coupled heat and mass transport model. A novel alternative formulation for sorption isotherms, that is applicable to both normal and high strength concrete, is developed. Furthermore, the effect of the slip flow effect is included and several state equations, including relative permeability and saturation vapour pressure, are adopted. Additionally, the effect of polypropylene fibres as a spalling prevention technique is modelled via a modification of the intrinsic permeability formulation. The transport model is further coupled with a damage-based mechanical model for concrete. The fully coupled thermo-hygro-mechanical model is presented through validation and verification problems and case studies. The model is implemented in a finite element formulation and behaves in a robust manner. The predictions of moisture state for the benchmark problems of drying and heating compare well with experimental results. Classical behaviour associated with heated concrete, such as moisture clog, gas pressure build-up, etc. are all captured by the presented model. The thesis concludes by considering the analysis of prestressed concrete pressure vessel.
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Leung, Chun-yu Cliff, and 梁鎮宇. "Performance of in-situ concrete stitches in precast concrete segmentalbridges." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B49617758.
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Multi-span precast concrete segmental bridges are commonly constructed using the balanced cantilever method, which essentially involves sequentially extending precast segments outwards from each pier in a balanced manner. A gap of 100 to 200 mm wide is usually provided around the mid-span location between the last two approaching segments to facilitate erection. In-situ concrete is then cast to ‘stitch’ the segments together, thus making the bridge deck continuous. In the current practice, the in-situ concrete stitches are usually designed to be capable of sustaining considerable sagging moment but only minimal hogging moment. Failure of stitches may occur under exceptional circumstances that may potentially trigger a progressive collapse. However, relatively little research in this area has been carried out.
In view of this, the author is motivated to undertake an extensive study of the behaviour of in-situ concrete stitches and the effects of their performance on the robustness of typical segmental bridges. Experimental study is carried out to examine the behaviour of in-situ stitches under different combinations of internal forces. Series of stitch specimens of different configurations are tested. Subsequent parametric studies are conducted numerically to examine the effects of various parameters on the load-displacement characteristics of the stitches. Formulae for strength estimation are proposed based on the results.
A study of robustness involves analyzing the collapse behaviour of a structure in an extreme event and the analysis should be carried out up to and then well beyond the state of peak strength of structural members. A finite element programme for post-peak analysis is therefore developed for the present study. As the ability of a member section to sustain large inelastic deformation can ultimately affect the robustness of a structure, an investigation is conducted to examine the effects of steel content, yield strength and prestressing level on the ductility and deformability of prestressed concrete sections.
Using the programme developed, the formation of collapsing mechanisms of a multi-span segmental bridge deck in an extreme event is examined. A typical bridge deck is subject to prescribed accidental load on its span in order to analyze the sequence of failure. Substantial redistribution of internal forces along the deck is observed as failures initiate, thus causing subsequent failures of other deck sections even though they have been designed to resist the internal forces at the ultimate limit state. The results indicate that any span of a multispan bridge may become a temporary end-span in the event of collapse of an adjacent span and the strength of the sections must be designed accordingly to prevent progressive failure. As a span becomes a temporary end-span, the in-situ concrete stitches may experience substantial moment and shear, and their failure could potentially trigger progressive collapse of the entire bridge deck.
Towards the end of the thesis, important design considerations that can enhance the performance of in-situ concrete stitches and robustness of precast concrete segmental bridges are presented.published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy