Experimental Research On Impact Resistance And Crack Resistance Of Layered Hybrid Fiber Reinforced Concrete

Plain concrete, fly ash concrete, polypropylene fiber concrete, steel fiber reinforced concrete, layered steel fiber reinforced concrete, hybrid fiber reinforced concrete, and layered hybrid fiber reinforced concrete was studied on compressive strength test, free-fall hammer impact resistance test and early-age plastic crack resistance test.Three specimens were made for each group in twenty-eight days compressive strength test. The test results showed that10%fly ash slightly reduced the compressive strengths of concrete, polypropylene fibere basically had no effect on compressive strength of concrete, steel fiber made compressive strength of fly ash concrete improved by5.11%, layered steel fiber made compressive strength of fly ash concrete improved by3.51%, compressive strength of hybrid fiber reinforced concrete was improved by10.22%than fly ash concrete, and compressive strength of layered hybrid fiber reinforced concrete was improved by4.47%than fly ash concrete.Φ152mm×63.5mm of round cake shape specimen was used in free-fall hammer impact resistance test.The test results showed that the initial crack and failure impact resistance times of plain concrete were both small and almost equal, the initial crack and failure impact resistance times of fly ash concrete were slightly higher than plain concrete, but the two kinds of concrete all showed brittle failure characteristics. The initial crack and failure impact resistance times of polypropylene fiber concrete were respectively2.19times and2.41times of fly ash concrete. The initial crack and failure impact resistance times of steel fiber reinforced concrete were respectively2.27times and3.54times of fly ash concrete. The initial crack impact resistance time of layered steel fiber reinforced concrete was relatively low, but the failure crack impact resistance time was very high, and were respectively1.71times and3.22times of fly ash concrete. The processes of failure impact resistance presented certain plastic failure characteristics for polypropylene fiber concrete, steel fiber reinforced concrete, layered steel fiber reinforced concrete. The initial crack and failure impact resistance times of hybrid fiber reinforced concrete were respectively4.07times and5.12times of fly ash concrete, The initial crack and failure impact resistance times of layered hybrid fiber reinforced concrete were respectively3.66times and4.68times of fly ash concrete, and the two kinds of concrete all showed plastic failure characteristics with more fine cracks.600mmx600mmx63mm of rectangular plate specimen was used in early-age plastic crack resistance test.The test results showed that early cracking phenomenon of plain concrete was serious with larger number, longer length, wider width, and fracture distribution was more complicated with some vertical the edge, some along the diagonal direction, and some through. Controlling the concrete cracking phenomenon effect was not obvious for10%fly ash. Polypropylene fiber reduced the crack number, length, and width of the concrete to some extent, with basic perpendicular to the plate edge distribution, and the crack reduction coefficient was56.56%, anti-cracking grade was the second grade. Cracking phenomenon of steel fiber reinforced concrete and layered steel fiber reinforced concrete was reduced to a certain degree, and crack usually distributed along the vertical plate edge direction, and the crack reduction coefficient of the two kinds of concrete is respectively47.05%、43.24%, anti-cracking grade was the third grade. For hybrid fiber reinforced concrete, and layered hybrid fiber reinforced concrete, the crack number is significantly reduced, the crack length was significantly shortened, the crack width became finer, and the cracking time was significantly delayed. And the crack reduction coefficient of the two kinds of concrete was respectively95.15%,93.07%, anti-cracking grade was the first grade.Figures47tables14references62...