In this experimental study, a mechanical and economic analysis has been done to investigate the performance of recycled steel fibers (RSF) from waste tires. Two types of recycled fibers, including recycled steel fibers with impurities (with a high amount of rubber and textiles) (RSFI) and clean recycled steel fibers (CRSF), have been investigated. Recycled fiber\\\\\\\\\\\\\\\'s performance has been compared to industrial steel fibers (ISF); these fibers have hook ends. The mechanical properties of normal concrete and concrete reinforced with steel fibers, including compressive strength, splitting tensile strength, and flexural strength, were investigated at ambient temperature and temperatures of 200 °C and 600 °C. The results showed that at ambient temperature and 200 ℃, RSFI decreases the compressive strength of concrete due to the high amount of rubber and textiles, while CRSF has shown results comparable to ISF at all temperatures. The positive effect of RSFI has been observed at 600 ℃ by melting rubber and burning textiles. The specimens reinforced with steel fibers, regardless of their type, improved the tensile strength and modulus of rupture compared to the control specimen at all temperatures. RSFI has shown poorer performance compared to ISF and CRSF. The mechanical and economic analysis showed that CRSF could be a suitable alternative to ISF to strengthen concrete mixtures.

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