Research On Mechanical Properties Of Hybrid Fiber Reinforced Concrete

Hybrid fiber reinforced concrete(HFRC)is a composite multiphase materials which incorporated two or more kinds of fibers into the concrete, and is to improve the performance of concrete by the use of different fiber characteristics. Compared to single fiber reinforced concrete, hybrid fiber reinforced concrete used different fibers in a complementary role of each loading stage to improve the performance of concrete. Meanwhile, the hybrid fiber can reduce the amount of fiber, and reduce project cost. Fiber hybrid also can reduce mechanical strength of concrete, namely “negative confounding effect”. Thus, a comprehensive and systematic experimental study for the mechanical properties of hybrid fiber reinforced concrete is particularly necessary.Several common high elastic modulus fibers(Steel fibers, basalt fibers, polyvinyl alcohol fibers) and low elastic modulus fibers(Polypropylene fiber and mesh polypropylene fiber) are incorporated into the concrete, and its cube compressive strength, axial compressive strength, elastic modulus, Poisson's ratio, flexural strength, splitting tensile strength and shear strength are studied. The test results are as follows:1. The mechanical properties of hybrid steel fiber-mesh polypropylene fiber reinforced concrete are excellent, and the cube compressive strength, axial compressive strength, splitting tensile strength, flexural strength and shear strength respectively increase than plain concrete by 2.8%, 3.9 %, 26.5%, 27.7%, 24.7%.2. Doped single basalt fiber or polypropylene fiber and basalt fibers hybrid has little effect on the mechanical properties of concrete.3. Polyvinyl alcohol fiber and polypropylene fiber hybrid exhibit negative confounding effect on concrete, its splitting tensile and flexural strength respectively are reduced by 17.8%?12.9%, than the single-doped polyvinyl alcohol fiber concrete. The mechanical properties of hybrid Polyvinyl alcohol fiber- mesh polypropylene fiber reinforced concrete are improved to varying degrees, its cube compressive strength, axial compressive strength, splitting tensile strength, flexural strength and shear strength respectively are increased by 3.2%?3.3%?5.9%?6.1%?0.3%, than plain concrete.4. Single fiber and hybrid fiber will improve the integrity of the concrete at failure, steel fiber and mesh polypropylene fiber are often pulled out, and polypropylene fibers are across the failure surface of concrete.5. Polypropylene fiber and mesh polypropylene fiber are not unanimous with high elastic modulus fibers on mechanical properties of concrete, such as the compressive strength and splitting tensile strength of hybrid steel fiber and polypropylene fiber reinforced concrete increase by 6.4%, 3.7%, and the compressive strength and splitting tensile strength of hybrid steel fiber and mesh polypropylene fiber reinforced concrete by 2.8%, 26.5%.6. Single fiber and hybrid fiber have little effect on the concrete elastic modulus and Poisson's ratio. After the incorporation of different fibers, elastic modulus and Poisson's ratio of concrete have a small change in 3.6% and 4.9%.