Evaluation of various content of steel fibers on improving the mechanical and durability properties of concrete at high temperatures

One of the factors of damage and destruction of concrete structures is fire. Concrete structures, in addition to having the proper mechanical characteristics, they must have durability properties to use their capacity over their lifetime. In this study, the effect of various volume fraction of steel fibers on improving the mechanical and durability properties of concrete at various temperatures has been investigated. Mechanical properties including compressive and tensile strength of concrete in the hot condition and the durability characteristics of the concrete after cooling, including surface water absorption, the penetration depth of water, electrical resistance and weight loss have been investigated. This study covers 0.25 and 0.50% volume fraction of steel fibers and temperatures of 28 to 800 ° C. The results show that the increase in compressive strength and tensile strength due to the age of the samples was higher in fiber concrete than non-fibrous concrete. It was also observed that the addition of 0.25 and 0.5% of steel fibers at the tested temperatures improved the compressive and tensile strength in the range of 10 to 27% and 8 to 200%, respectively. In addition, application of these fibers has reduced the sorptivity coefficient, the penetration depth of water, the electrical resistance of concrete and the weight loss of concrete owing to the high temperature. The results of this study showed that, at temperatures below 500 °C specimens containing 0.25% of steel fiber and 500 °C onwards, specimens containing 0.50% of steel fiber had the best performance on the improvement of the mechanical and durability properties of normal concrete at high temperatures.