Contribuição ao estudo da durabilidade e do transporte de fluidos em concretos contendo adições minerais

• Autor(a) principal: Almeida, Marina Augusta Malagoni de
• Data de Publicação: 2016
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tede/7271
• topic: Mecanismos de transporte; Durabilidade; Sílica ativa; Nanossílica; Metacaulim; Transport mechanisms; Durability; Silica fume; Nanosilica; Metakaolin; ENGENHARIAS::ENGENHARIA CIVIL

Brazil's current water crisis, generated by the low level of reservoirs, has threatened the national energy production. Faced with this problem, the wind towers present themselves as a viable solution. It is known that these towers are constructed in regions of high aggressiveness and therefore, it is necessary to develop high performance concretes that are able to withstand environmental action to which they are submitted, so that these structures reach the lifespan previously defined in project, ensuring the viability of the towers. In this sense, the present study evaluates the mass transport mechanisms (permeability and absorption) that takes place inside the concrete containing mineral pozzolanic admixtures of high performance, in order to evaluate the influence of the presence of these additions in these properties. Three different study mixes were prepared containing, respectively, 9% of silica fume in composition with 1% of nanossílica, 5% of a metakaolin with high fineness in composition with 5% of a metakaolin slightly less fine, both with high pozzolanic activity, a mix containing only 10% of the metakaolin with higher fineness, and a reference proportioning. The analysis presented in this work involve the scanning electron microscope (SEM) to characterize the internal structure of the material, the trace reconstruction test to analyze the aggregate/binder ratio in the regions of the cover and the interior of concrete, and the analyzes related to the mass transport: water absorption by immersion and capillarity and the air permeability obtained by the Figg’s method, in addition to the mechanical characterization. The concrete with addition of pozzolanic admixtures showed significant improvements in compressive strength, in the modulus of elasticity, in the air permeability and in the refinement of pores. Furthermore, the evaluation of the microstructure by scanning electron microscope showed that the use of mineral admixtures may cause an improvement in the adhesion and in the densification of the transition zone between aggregate and cement paste. The trace reconstitution test showed that the concrete cover has lower ratio aggregate/binder, which corroborates the results of the capillary absorption test in which it was found that the cover of concrete presents a mean capillarity absorption lower than the interior region. Thus, it was concluded that the incorporation of the different mineral admixtures studied in this work significantly alter the properties of concrete, with positive emphasis on the properties related to the durability, in which the benefits of using mineral admixtures is more pronounced and, in addition, it was also concluded that the concrete cover presents itself more favorable to the durability than the interior region.