Effect of waste steel fiber use on concrete behavior at high temperature

Recently, recycling of waste vehicle tyres which pose a significant risk to environmental health has become an important research issue due to environmental concerns worldwide. To handle the waste tyre pollution problem, recycling waste into new products and using waste to improve other materials' properties can be considered. Waste vehicle tyres can be used in the production of energy and various materials, providing economic and environmental advantages. In this study, experimental studies were carried out on the use of waste tyre steel fiber (WS) obtained from the recycling of heavy vehicle tyres in concrete, including the goal of recycling and reducing the need for raw materials. In one experimental group, waste tyre steel was added to concrete at 0.4% by volume instead of fine aggregate, while in the other experimental group it was added at 0.8% by volume. In the study, in addition to mechanical analyses, many microanalysis experiments were carried out to understand whether there was a strong relationship between the results. The study was conducted at target temperatures of 400, 600 and 800 oC depending on the fire scenario for building and construction materials according to ISO 834 and ASTM E119 standards. Compressive strength losses and characterization changes in 15 cm cube plain concrete and composite concrete specimens exposed to targeted high temperatures for 60 minutes were compared in terms of strength. Ultrasonic pulse velocity (UPV), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential thermal analysis (DTA), X-ray diffraction analysis (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis was also performed, as it was understood that there was not enough data in the literature regarding waste tyre steel fiber reinforced concrete. General results showed that fiber-added concrete made significant contributions to concrete performance at high temperatures.