Ternary Superposition Mix Design Method For Hybrid Fiber Reinforced Concrete

The workability of fresh concrete and mechanical behaviors of hardened concrete will bechanged by blended concrete with steel fiber and polypropylene fiber. Compared withordinary concrete, it is more complex to deal with hybrid fiber reinforced concrete mixtureratio design. In fact there is great different about the test rules of hybrid fiber reinforcedconcrete according to the results from the researchers in the globe. Most studies used themethod of orthogonal experiment and directly mix fibers in the concrete at present. Withincreasing of steel fiber and polypropylene fiber, concrete slump will be decreased and thework performance will be worse. It is not conducive to the construction. Though the latestrevised code[9](Technical Specification For Fiber Reinforced Concrete Structures, CECS38；2004, China) have added the specifications about synthetic fiber and steel fiber reinforcedconcrete, but there is still blank in the field of hybrid fiber reinforced concrete.To avoid the various design results according to the current technical specification bydifferent designer, the formulas of ternary superposition mix design method about hybrid fiberreinforced concrete is suggested in this paper and is verified by the test using this method todesign HF40, HF50and HF60hybrid fiber reinforced concrete mixture ratio. To study theeffects of steel fiber and polypropylene fiber on work performance and basic mechanicalbehaviors, the tests include fresh concrete slump，cube compressive strength, splitting tensilestrength, bending tensile strength, axial tensile strength and flexural toughness.It shows that mixture ratio design method based on ternary superposition can meet therequirements of work performance and basic mechanical properties of concrete. And ascientific basis for revising hybrid fiber concrete mixture ratio design method is provided.