Study On The Impact Properties Of Hybrid Fiber Reinforced Concrete

In recent decades, due to its excellent properties, Hybrid Fiber Reinforced Concrete (HFRC) becomes one of the new concrete materials which attract much attention in civil, architecture and bridge application fields. The designable properties of HFRC to satisfy the different applications by using different mix ratios of different kinds of fibers make it superior. Former studies show that, addition of steel fiber can improve the tensile strength, flexure strength and shear strength of concrete significantly; and addition of polypropylene fiber, another kind of fiber popular used in applications, largely decreases the brittle behavior of concrete. The effect of polypropylene fiber is represented by crack resistance; this gives a solution to crack tendency due to the brittleness of concrete and does an important role in bettering the inner structure of concrete.In the thesis, the mix ratios of HFRC are designed and studied to meet the demands of bridge deck pavement. The influence of cement strength grade, steel fiber and polypropylene fiber contents on HFRC's quasi-static compressive strength, flexure strength, flexure toughness and dynamic properties is primarily concerned. The properties of Plain Concrete (PC) and Steel Fiver Reinforced Concrete (SFRC) under the same fundamental mix ratio are compared and analyzed with that of HFRC. The main contents include:(1) Compressive and flexure tests were carried out to test the performances of PC and HFRC samples molded with high quality cement. The study found that the reinforced effects of fibers to the compressive strength of high grade concrete are not obvious, but improve the flexure strength and flexure toughness obviously.(2) A split Hopkinson pressure bar was used to study the mechanics response of PC, SFRC and HFRC with three fiber contents. The damage phenomena of three materials under different impact velocities were observed, which shows that HFRC having a better impact resistance than SFRC and PC. Strain effects, energy absorption by unit volume, impact damage of the three materials under impact loading are compared. The results show that HFRC has better impact properties than SFRC and PC.(3) In order to normalize the application of HFRC material on bridge deck pavement, the production procedure, working flow and methods were established for the construction organization. The bridge deck pavements of a bridge and road testing sections have been paved by use of HFRC, the serving result of HFRC has been observed for half a year. The HFRC pavements remain in good conditions, which shows HFRC material is an ideal material for bridge deck pavement.