Durabilidade de compósitos cimentícios de ultra alto desempenho com incorporação de pó de vidro frente à ação de cloretos
Soares, Silvete Mari
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Reinforced concrete is one of the most widely used construction materials in civil construction, in Brazil and worldwide, due to the ease of taking on different shapes and for protecting the reinforcement from external actions and, thus, guaranteeing its durability. In order to build more resistant and durable structures, reinforced concrete started to be studied not as a material of high mechanical resistance, but as a material of high performance. High performance concrete (HPC) is a concrete with high mechanical resistance and with characteristics that guarantee its greater durability in the face of aggressive environments, among other requirements. Ultra high performance concrete (UHPC) is a material that has low permeability to chlorides, moisture and oxygen with a matrix composition that has a low water / binder ratio and, therefore, exhibits high mechanical performance and against corrosion of the reinforcement, be used to repair concrete structures. UHPC is generally designed with a high cement content, ranging between 800 and 1,000 kg/m3, which affects production costs, consumes natural sources of raw material and negatively affects the environment through 〖CO〗_2 emissions. Supplementary cementitious materials (SCM) have been widely used to partially replace Portland cement in concrete, both as filling material and as pozzolanic material. In this sense, glass powder is a good alternative due to its silica-rich nature and the large amount available that, in many cases, is disposed of in landfills or not, inappropriately. The hypothesis considered is the feasibility of using glass powder at high levels to replace Portland cement, maintaining the characteristics of high mechanical resistance and durability against the action of chlorides in ultra high performance cementitious composites, providing a reduction in the consumption of Portland cement. This work is justified by the better knowledge of the use of recycled glass powder in the ultra high performance cementitious composite, especially with regard to durability against chlorides, with the analysis of several factors and possible problems that this partial substitution may cause. The general objective is to evaluate the influence of the substitution of Portland cement by different levels of recycled glass powder in an ultra high performance cementitious composite in the mechanical resistance and durability against the attack by chlorides, being one of its specific objectives to determine the ideal content of glass powder to be incorporated into cementitious composites. Cementitious composites with different contents of recyclable glass powder were developed (0%, 10%, 20%, 30% and 50%). For that, mechanical tests were carried out and related to durability, such as: water absorption, resistance to chloride penetration, penetration front, total chloride content, chloride diffusion and migration, electrical resistivity and corrosion potential of cementitious composites. Regarding the microstructure, X-ray diffraction tests, thermogravimetry, scanning electron microscopy and computed tomography were performed. The mechanical results obtained were favorable to the incorporation of glass powder at high contents, since the mechanical strength remain high. Regarding the durability against the attack of chloride ions, the results were also favorable to the incorporation of high contents of substitution of Portland cement by glass powder, indicating a high capacity of CUAD to protect steel against the action of chloride ions. And finally, it is recommended to use the 50% content of incorporation of glass powder to replace Portland cement because it has high mechanical resistance, high resistance to attack by chlorides, in addition to the use of these cementitious composites contributes to the reduction environmental pollution, since the studied incorporations are waste.
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