Study On Flexural Properties Of Hybrid Fiber Reinforced Concrete In Sulfate Attack Environment

With the continuous advancement of "One Belt,One Road" strategy for Chinese policy,the number of concrete structures serving in sulfate and other hard environments continue to increase,which leads to the durability problem of structures.So it is imperative to improve the durability of concrete.Hybrid fibers can improve the flexural properties of concrete at multiple angles and levels,and the crackinhibiting ability slow down the corrosion of sulfate ions to concrete to a certain extent,then improve the durability of concrete.Therefore,the using of hybrid fibers has significant engineering application value.In this study,steel fibers and imitation steel fibers were adopted,and explored the effect of the corrosion ages,fiber types,volume contents of steel fiber,volume contents of imitation steel fiber,strength grades of concrete matrix under sulfate attack environment(dry-wet cycle,full immersion)on the flexural performances.According to the concrete failure forms,compressive strength,flexural strength and bending performances,the main research conclusions are as follows:(1)With in four months of erosion ages,the compressive strength,flexural strength,and flexural toughness of plain concrete,imitation steel fiber reinforced concrete,steel fiber reinforced concrete,and hybrid fiber reinforced concrete all showed an increasing trend with the increase of erosion age,which began to decline after four months of erosion age.After six months of erosion,the decline of plain concrete was more obvious,and its mechanical properties were lower than those of the non-eroded state,while the decline of hybrid fiber concrete was the smallest,and its mechanical properties were higher than the un-eroded state.(2)When the volume content of imitation steel fiber is 0.6%,and the erosion age is four-six months,with the increase of the volume ratio of steel fiber,the compressive strength,flexural strength and bending toughness of the hybrid fiber concrete gradually decrease.Slowing down,steel fibers can significantly improve the sulfate resistance of concrete.(3)When the volume content of steel fiber was 0.8% and the erosion age was from four to six months,with the increase of the volume contents of the imitation steel fiber,the decline range of the compressive strength,flexural strength and bending toughness of the hybrid fiber concrete increased first and then decreased.When the volume content of the imitation steel fiber was 0.6%,the improvement effects were the best,but the overall improvement effect was lower than that of the steel fiber.(4)After four to six months of sulfate erosion,the decline ranges of various mechanical indexes of hybrid fiber concrete slowed down with the increase of concrete matrix strength.Improving the strength grades of matrix concrete were beneficial to improve the resistance to sulfuric acid corrosion of concrete.(5)During the six month erosion age,compared with full immersion in sulfate,the deterioration of dry-wet cycles had a more obvious effect on the compressive strength,flexural strength and flexural toughness of hybrid fiber reinforced concret.