Effect of hybrid steel, polypropylene, polyvinyl alcohol, and jute fibers on the properties of ultra‐high performance fiber reinforced concrete exposed to elevated temperature

Abstract Evaluation of the effects of different fiber types with different ratios on the mechanical properties and explosive spalling prevention of Ultra‐High Performance Fiber Reinforced Concrete (UHPFRC) at elevated temperatures is the primary objective of the experimental work. Several fiber types, including steel fiber, polypropylene fiber, polyvinyl alcohol fiber, and natural jute fiber were used. Eight UHPFRC mixes were cast comprising the different hybrid fiber types. The results show that replacing polypropylene, polyvinyl alcohol, and jute fibers with steel fiber decreases the fresh and hardened properties of unheated UHPFRC while increasing durability. The existence of hybrid fibers improves the fire resistance of UHPFRC and fully prevents explosive spalling because of a considerable improvement in permeability. According to the test results, the optimum replacement ratio for UHPFRC mix is to replace polyvinyl alcohol fiber with an equivalent volume fraction of steel fiber, as it has a slight influence on the mechanical properties and prevented explosive spalling.