Research On The Flexural Toughness Of Hybrid Fiber Reinforced Concrete

Mixing the steel fiber and polypropylene monofilament fiber in high strengthconcrete can significantly improve the matrix concrete’ toughness and reduce itsbrittleness. But SF/PPF HFRC also owns the weakness of higher construction cost,larger weight and the difficulties of fibers’ dispersion. As a new type of fiber reinforcedmaterial, modified polypropylene fiber has wonderful effect of strengthening andtoughening. In order to develop the potential of steel fiber and polypropylenemonofilament fiber further, the three different fibers was mixed. And this well besignificance to improve the concrete’s toughness. In this paper the experimental researchand theoretical analysis methods were both used. With total fraction of fiber by volumenot more than1%, the steel fiber, modified polypropylene fiber and polypropylene fiberchosen as three elements were used to be reinforcement in the concrete. The concrete ofCF50is made with the water ration of0.31. Based on the compressive test and splittingtensile test,the basic mechanical properties of HFRC is studied. And by the flexuraltoughness test on notched beams, the post-peak behavior were investigatedsystematically. The following studies were done:(1) Based on the compressive test and splitting tensile test on test cubes of150mm×150mm cross section, the basic mechanical properties of HFRC is studied;(2) Based on the flexural toughness test on notched beams with the section of150mm×150mm×550mm, the effect of fiber volume fraction and hybrid mode uponconcrete’s post-peak behavior were investigated;(3) By the deflection–CMOD(the displacement of the crack mouth) curves, theCrack control ability of the HFRC is analyzed;(4) According to the load–deflection and load–CMOD curves obtained by theflexural toughness test, the equivalent flexural tensile strength was calculated. By theanalyze of the equivalent flexural tensile strength, the flexural toughness was evaluate;(5) Based on the least squares principle, the function relation between the volumefraction of the steel fiber or modified polypropylene fiber and the equivalent flexuraltensile strength is built.