Estudo da influência das elevadas temperaturas sobre as propriedades mecânicas residuais e a durabilidade do concreto de alta resistência com e sem adição de fibras de polipropileno

• Ano de defesa: 2021
• Autor(a) principal: Heron Freitas Resende
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais
• Palavras-chave em Português: Construção civil; Materiais de construção; Concreto de alta resistência; Fibras de polipropileno; Altas temperaturas; Propriedades mecânicas; Durabilidade (Engenharia)
• Link de acesso: https://hdl.handle.net/1843/38137

Structural elements when used in civil construction must be designed to meet the requirements of mechanical performance, durability, and fire resistance. The main attributes of high-strength concrete (HSC) are its greater mechanical strength and durability, which are fundamental to the performance of a building. However, given its low porosity, the HSC has lower fire resistance when compared to normal strength concrete (NSC), i.e., it is more prone to rupture, usually explosive, exposing the structure's reinforcement. Therefore, this work aims to study the influence of high temperatures on the residual mechanical properties and the durability of HSC with and without the addition of polypropylene fibers, as well as to analyze the possible occurrence of spalling. For this, tests were performed on cylindrical specimens in heating furnaces for increasing temperatures, which varied from 100 °C to 800 °C at a constant heating rate of 1 °C/min, remaining for 60 minutes at the pre-established temperature and then being submitted to a constant cooling rate of 1 °C/min. Subsequently, destructive and non-destructive tests and laboratory analyses were performed. When compared to the HSC without the use of fibers, the results showed that the use of 2 kg/m3 of polypropylene fibers in the HSC improved the compressive strength up to the temperature range of 400 °C and the tensile strength up to around 200 °C, while at room temperature there was a slight increase in the elastic modulus. The efficiency of the use of polypropylene fibers in the HSC was also verified in the results of durability tests, such as ultrasound up to approximately 200 °C, as well as improvements in the results of the electrical resistivity test up to the temperature range of 400 °C. On the other hand, in the absorption and mass loss tests, the HSC without the use of fibers performed better. At high temperatures, the results showed that the performance in residual mechanical properties and durability between the HSC with and without polypropylene fibers are practically similar. In the physical observation of the surface of the samples after the heating test between 600 °C and 800 °C, it was possible to identify how the use of polypropylene fiber in the HSC leads to reductions in cracks and pores on the surface when compared to the HSC without the use of fibers. As for the microstructure analysis, it was verified the appearance of channels in the concrete structure by the melting of polypropylene fibers after the heating test of the HSC with fibers samples. In addition, there was no spalling in any heating test for the HSC samples with and without polypropylene fibers.