Experimental Study On The Flexural Toughness Of Hybrid Fiber Reinforced Shotcrete

For the shotcrete which was one type brittle material,mixing with hybrid fiber could help improve its toughness.Domestic and foreign researchers often used the flexural toughness as an significant index to evaluate the toughness of hybrid fiber reinforced shotcrete,and the test specimens they adopted frequently were beam specimens.But beam specimens were not fit practical uses of hybrid fiber reinforced shotcrete,the beam ways which were used to assess the flexural toughness of hybrid fiber reinforced shotcrete also had some weaknesses.Compared with beam specimens,panel specimens were more closer to practical applications of hybrid fiber reinforced shotcrete,and the ways which were based on panel specimens could not only reflect the flexural toughness of hybrid fiber shotcrete more objectively and accurately,but also provide better theoretical references for the design and construction of hybrid fiber reinforced shotcrete.But with the relevant ways were wrote into the standard test methods for fiber reinforced concrete of our country relatively late,domestic researchers got fewer research findings which were based on panel specimens.By designing a type connection device for fixing the displacement meter and choosing the method which was to mix different content of steel fiber,polypropylene fiber and blast furnace powder to make hybrid fiber reinforced shotcrete panels,the paper conducted the following studies:(1) The research on the compression strength of hybrid fiber reinforced shotcrete was conducted,the results showed that:In comparison to polypropylene fiber, the contents change of steel fiber and blast furnace powder could improve the compression strength of hybrid fiber reinforced shotcrete greater.(2) Based on the experiments for the flexural toughness of circular panel and the experiments for the flexural toughness of square panel,the rule that flexual toughness of hybrid fiber reinforced shotcrete vary with the contents of fiber was studied,and the failure mode of panels was discussed, the results showed that:With adding more steel fiber,the flexual toughness of hybrid fiber reinforced shotcrete would increase;After mixing small contents of polypropylene fiber,the flexural toughness of steel fiber reinforced shotcrete could improve obviously;All of hybrid fiber reinforced shotcrete panels where the cracks appeared but not ran through presented ductile failure.(3) Based on the experiments for the flexural toughness of square panel, the rule that flexual toughness of hybrid fiber reinforced shotcrete vary with the contents of blast furnace powder was studied, the results showed that: With adding more blast furnace powder,the flexural toughness of the hybrid fiber reinforced shotcrete would increase.(4) After contrasting and analyzing test dates and failure pictures which got from two different test methods for the flexural toughness of panel,there were obvious similarities between the change rules of tests and the failure modes of specimens obtained from two tests.