RESUMOEsse trabalho apresenta um estudo comparativo do comportamento mecânico de vigas pré-moldadas de concreto armado convencional (CCP), fabricadas por uma empresa local e de concretos geopolimérico de metacaulim (CCG) e geopolimérico com 20% de cinza volante e silicato de cinza de casca de arroz (CCG-20CV-CCA), como matrizes substitucionais. Os resultados mostraram que os concretos geopoliméricos apresentaram comportamento similar ao do CCP, na mesma classe de resistência do concreto, taxa de armadura e disposição das armaduras no elemento estrutural estudado. O uso das cinzas promoveu aumento do módulo de rigidez à flexão e dos limites de deformação das vigas geopoliméricas, em especial para a CCG-20CV-CCA sob a maior taxa de armadura. Os padrões de fissuração e os modos de ruptura encontrados foram similares àqueles mostrados pelo CCP, com a conclusão, neste estudo de caso, de que as vigas pré-moldadas, como fabricadas pela empresa, foram superarmadas ao longo do bordo superior. Embora o dimensionamento da viga não tenha sido objeto deste estudo, foi mostrado que o concreto geopolimérico pode substituir plenamente o CCP, em concreto armado, abrindo oportunidade de uso dos mesmos códigos de dimensionamento desenvolvidos para este material tradicional. Palavras-chave:Geopolímero. Pré-moldado. Concreto armado. ABSTRACTThis work presents a comparative study of the mechanical behavior of precast concrete beams (CCP), manufactured by a local company and geopolymer concrete of metakaolin (CCG) and geopolymer concrete with 20% of fly ash and rice husk ash silicate (CCG-20CV-CCA), as substitutional matrices. The results showed that the geopolymer concretes presented similar behavior to the CCP, in the same class of concrete strength, reinforcement rate and arrangement in the structural element studied. The use of the ashes promoted an increase of the flexural stiffness modulus and the limits of deformation of the geopolymer beams, in particular for the CCG-20CV-CCA under the highest reinforcement rate. The cracking patterns and failure modes found were similar to those shown by CCP, with the conclusion, in this case study, that precast beams, as manufactured by the company were super-reinforced along the top of the beams. Although the dimensioning of the beam has not been the object of this study, it has been shown that the geopolymer concrete can completely replace the CCP in reinforced concrete, opening up the opportunity to use the same structural design codes developed for this traditional material.
The addition of certain pozzolanic materials to Portland cement significantly changes the properties of the hardened matrix. If it has too high content of blast furnace slag, as the case of blast furnace Portland cements (BFPC), the early and late compressive strengths can be severely delayed or reduced. The objective this work was to investigate the potential of alkali-activation of BFPC and metakaolin (MK) blends by different types and contents of alkali-activators. The results clearly showed the influence of the MK pozzolanic activity and the type and content of activator used, in the development of compressive strengths of BFPC-MK blends. Microstructural analysis by SEM/EDS, DSC and XRD shown that the consumption of portlandite and the extra formation of C-S-(A)-H phases are the main positive effects registered. However, MK also promotes the formation of ettringite and unstable hydrated calcium aluminate phases, which, with the course of hydration, undergo a change in structure and volume loss, contributing to the reduction of final strengths. Content of 25% MK and 7.5% Na2SiO3 provided the best mechanical strength. The microstructures formed showed greater formation of ettringite, however there was also a reduction in portlandite and massive formation of C-S-H and C-S-(A)-H products.
As fundações estão sujeitas à deslocamentos verticais ou inclinados, algumas em maior ou menor grau, a depender da interação solo-estrutura. Esse fenômeno é denominado recalque e pode ser ocasionado por diferentes fatores, sendo um deles a presença ou a supressão de árvores próximas às edificações, provocando movimentos não previstos e o surgimento de fissuras. Além do recalque, o desenvolvimento das raízes pode levantar estruturas leves, como os pisos, e danificálos. Assim, este artigo teve como objetivo avaliar os danos causados por árvores frutíferas próximas à uma edificação unifamiliar. Por anamnese, foram obtidas informações sobre o histórico da edificação, o plantio das árvores (abacateiro e goiabeira) e a supressão do abacateiro. Já as fissuras foram aferidas, monitoradas e avaliadas, a fim de verificar suas atividades, determinar o caráter dos danos e as possíveis causas. O desenvolvimento das raízes destas árvores foi o fator que gerou as fissuras, bem como a modificação de umidade do solo, proporcionando o deslocamento da fundação sob o pilar analisado. Devido ao desconhecimento do tipo de solo, não foi possível correlacionar os danos com a supressão do abacateiro. Contudo, o recalque se mostrou estabilizado e as fissuras não interferem no uso ou na estabilidade da estrutura.
This article consists of an explanatory contribution of BIM (Building Information Modeling) methodology applied during the project’s compatibility in the modeling stages of the various specialties that may be included in a specific project. Therefore, bibliographical research was carried out describing the incompatibilities found by other authors and a case study developed in Revit software by the authors of this review. The main objective was to promote knowledge of the importance of spatial visualization provided by BIM software in reducing construction problems, while emphasizing the immediate need for the technology to be disseminated in the civil construction sector. Currently, the sector still adopts limited techniques that are prone to numerous errors. Accordingly, BIM is considered the recent technological innovation for the project of buildings. Thus, the existing interferences between the projects are easily identified for the adaptation of elements towards conformity.
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