Análise da perda de resistência do concreto leve, com argila expandida e fibras de polipropileno, após exposição a elevadas temperaturas

Abstract

Concrete is a worldwide consumed material due to its fresh state easy moldability and its properties when hardened, such as strength and durability. It also presents good thermal performance, due to its incombustibility to low thermal conductivity. In this context, the behavior of lightweight concrete with polypropylene fibers addition after exposure to temperatures of 300 °C, 600 °C and 900 °C for 90 minutes, simulating a fire situation, was the object of this study. Seventy two cylindrical concrete specimens, 5 centimeters in diameter and 10 centimeters of height, were molded for three different water/cement ratios: 0.45, 0.50 and 0.5. After seven days, each mix ratio was submitted to the fire simulation test for the three temperatures and, after slow cooling, the specimens were analyzed for specific mass and appearance, and then ruptured on the eighth day. The higher the temperature at which the concrete was exposed, the lower its specific mass and, consequently, the compressive strength. For the temperature of 900 °C, its resistance was less than 25% of the original resistance. Polypropylene fibers improved the performance of the concrete to the ambient temperature and to the temperatures of 300 °C and 600 °C, reducing cracking and increasing its compressive strength. In addition, the occurrence of spalling was not observed for fiber-added concrete.