This work presents a study about the viability of possible CO 2 emissions reductions scenarios for the cement manufacturing through the implementation of Clean Development Mechanisms (CDM) associated with the partial replacement of cement by sugar cane bagasse ash (SCBA). Studies on the thermal, chemical and mechanical behavior of concretes containing 5 to 20% of ash indicated that there is improvement on the performance of all analyzed properties and that the ash can be used as admixture on the cement manufacturing. The CO 2 emissions of two hypothetical scenarios of CDM Project implementation in the state of São Paulo through this technology were evaluated based on the official and applicable methodology. The results show that there are emission reductions on both scenarios, even for the most unfavorable, evidencing the possibility of obtaining negotiable carbon credits.Keywords: clean development mechanisms, CO 2 emissions, sugar cane bagasse ash, carbon credits.Este trabalho apresenta um estudo sobre a viabilidade de possíveis cenários de redução de emissão de CO 2 na fabricação de cimento através da implementação de projetos de Mecanismo de Desenvolvimento Limpo (MDL) associados à substituição parcial de cimento por cinza do bagaço de cana de açúcar (CBCA). Estudos sobre o comportamento térmico, químico e mecânico de concretos com 5 a 20% de cinza indicaram que existe melhora no desempenho de todas as propriedades analisadas e que a cinza pode ser usada como aditivo na fabricação de cimento. As emissões de CO 2 de dois cenários hipotéticos de implementação de projeto de MDL através desta tecnologia no estado de São Paulo, com base na metodologia oficial aplicável, foram avaliadas. Os resultados demonstram que existem reduções de emissões em ambos os cenários, inclusive para o mais desfavorável, evidenciando a possibilidade de obtenção de créditos de carbono negociáveis. Janeiro, toledo@coc.ufrj.br, eduardo@coc.ufrj.br, CT-Ilha do Fundão, 21945-970, Rio de Janeiro-RJ, Brazil; Civil Engineering Laboratory, Science and Technology Center, Universidade Estadual do Norte Fluminense Darcy Ribeiro, gcc@uenf.br, Av. Alberto Lamego, 2000, 28013-602, Campos dos Goytacazes -RJ, Brazil; c FBDS -Fundação Brasileira para o Desenvolvimento Sustentável, Rio de Janeiro, RJ, branca.americano@gmail.com. Received: 26 Mar 2010 • Accepted: 20 Jan 2012 • Available Online: 02 Apr 2012 Abstract Resumo Palavras
Civil construction is responsible for the excessive consumption of natural resources and the generation of the largest share of solid urban waste. In this context, recycling of construction and demolition waste (CDW) is presented as an alternative to minimize the impacts generated by construction. This study aimed to evaluate the influence of recycled CDW aggregates on the behavior of Portland cement mortars with three distinct mixtures. In addition to the reference mixtures, mortars with three different substitution levels of the natural aggregate for recycled aggregate, which were submitted to physical and mechanical tests in the Laboratory of Structures and Materials (LABEST) - COPPE/UFRJ. The results showed that for some substitution levels there was no loss on the properties of the mortars. Therefore, their performance is a function of the mixture adopted and the substitution content of the natural aggregate for the recycled.
ResumoComputational modeling has become a common activity to Civil Engineering researchers and professionals. Therefore, the knowledge about the mechanical behavior of materials is very important. To correctly model the mechanical behavior of concrete structures subjected to shear stress, it is necessary to determine the shear retention factor that accounts for the friction between the two surfaces of a crack. The objective of this study is to show how the shear retention factor of steel fiber reinforced concrete can be obtained from direct shear tests associated to computational modeling. A concrete matrix with compressive strength of 60 MPa, to which 1% and 2% content of steel fibers were added, was used for the shear tests. The stress-slip relationship was obtained from these tests, and the shear retention factor of the steel fiber reinforced concrete was determined from inverse analysis using the Finite Element Method software DIANA © 8.1.2. Finally, the shear retention factor and the influence of steel fibers on the cracks were validated from the computational modeling of steel fiber reinforced concrete beams subjected to shear available in the literature. Keywords: Shear, Steel Fiber Reinforced Concrete, Computational Modeling.A modelagem computacional cada vez mais se torna parte integrante das atividades dos pesquisadores e profissionais da área de engenharia civil. Para isso, o conhecimento do comportamento mecânico dos materiais é de fundamental importância. No caso das estruturas de concreto submetidas a esforços de cisalhamento, para a correta representação do seu comportamento é necessária a determinação do fator de retenção do cisalhamento. Neste trabalho, procura-se determinar esse fator para concretos reforçados com fibras de aço por meio de ensaios de cisalhamento direto em corpos-de-prova prismáticos associados à modelagem computacional. Foi estudada, em laboratório, uma matriz de concreto com resistência à compressão de 50 MPa, à qual foram adicionadas 1,0% e 2,0% de fibras de aço. A relação tensão versus deslizamento foi determinada experimentalmente, sendo em seguida realizada uma análise inversa dos corpos-de-prova de modo a se determinar o fator de retenção do cisalhamento do concreto reforçado com fibras de aço. Para tanto, foi utilizado o programa comercial de elementos finitos DIANA © 8.1.2. Ao final, o fator de retenção do cisalhamento, bem como a influência das fibras na fissuração, foi validado por meio da modelagem de vigas de concreto armado reforçado com fibras de aço submetidas a esforços de cisalhamento disponíveis na literatura. Aço, Modelagem computacional. Palavras-chave: Cisalhamento, Concreto Reforçado com Fibras de
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