An Experimental Study on the Effects of Adding Steel and Polypropylene Fibers to Concrete on Its Resistance after Different Temperatures

Abstract The use of fibers in concrete improves strength, ductility, and durability of concrete. Concrete has fireproofing properties, but rebars are the most important concern of reinforced concrete structures in the event of a fire outbreak. Therefore, one of the recommendations to reduce these risks is the use of alternative materials like fibers. In this article, the effects of different temperatures on the mechanical properties of concretes with different cement contents containing steel and polypropylene fibers were studied. The specimens were placed under temperatures of 25°C, 100°C, 250°C, 500°C, and 700°C, and the results revealed that the effects of fire on concrete containing steel fibers are more damaging. Also, the compressive strength and modulus of rupture at 25°C and tensile strength at 250°C have the maximum values. Compressive and tensile strengths of concrete containing steel fibers were 40 % and 50 %, respectively, more than the concrete containing polypropylene fibers. However, their flexural strength was almost equal. By comparing the flexural strength of specimens with grade 400 and grade 700, it can be concluded that the specimens with grade 400 have more resistance by about 10 to 40 %.