Effect of Hybrid Fibers on the Mechanical Properties of High Strength Concrete

In this study, high strength concrete of 75 MPa compressive strength was investigated. The experimental program was designed to study the effect of fibers and hybrid fibers (steel and polypropylene fibers) on the fresh (workability and wet density) and hardened properties (compressive strength, splitting strength, flexural strength and dry density) of high strength concrete. Results show that decreases in slump flow of all concrete mixtures containing steel, polypropylene and hybrid fibers compared with control mix (0 % fiber). Hybrid high strength concrete with steel and polypropylene fibers showed superior compressive, splitting, flexural strengths over the others concrete without or with single fibers content. The test results indicate that the maximum increase in compressive and flexural strengths are obtains with the hybridization ratio (70%steel + 30 % polypropylene) and were equal to 14.54 % and 23.34 % respectively, compared with the control mix. While, the maximum increase in splitting tensile strength with (100 % steel fiber +