Mechanical properties of recycled steel fiber reinforced ultra-high-performance concrete

Two types of recycled steel fiber from waste tires were used to prepare ultra-high-performance concrete (UHPC) containing coarse aggregate and their mechanical properties, including compressive strength, splitting tensile strength, fracture energy and static elastic modulus were determined. Plain UHPC without steel fiber and UHPC with different types of normal commercial steel fibers were also prepared for comparison. The results indicate that the recycled steel fiber without rubber particles has a slightly negative effect on the compressive strength of UHPC with a decrease of 3.91% and other types of steel fiber can improve the mechanical properties of UHPC. The recycled steel fiber with rubber particles significantly improves the fracture energy of UHPC and is approximately 4 times as high as that of the normal steel fiber. Additionally, the improvement of the recycled steel fiber on the splitting tensile strength and static elastic modulus of UHPC is superior to that of the normal steel fiber. This suggests that the recycled steel fiber especially that with rubber particles can be a toughening material used in concrete, and can substitute for the normal commercial steel fiber to be applied in UHPC engineering.