Experimental study on direct shear properties of polypropylene fiber concrete of different scales

Abstract In order to study the shear performance of polypropylene fiber concrete (PFRC), two kinds of polypropylene fine fiber and one kind of polypropylene coarse fiber were selected for incorporation combination, and the direct shear tests of polypropylene fiber concrete under different axial compressive stress were carried out. The damage pattern and shear stress-displacement curve of PFRC under direct shear load were analyzed, the shear damage mode and strength criterion of PFRC were studied, and the shear toughness enhancement effect of polypropylene fiber on concrete was investigated. The results showed that: when the axial compressive stress was below 4 MPa, the PFRC specimens were mainly damaged by slip; when the axial compressive stress was between 4MPa and 15MPa, the specimen mainly suffered shear failure, accompanied by slip failure. In the case of total fiber admixture of 3 kg/m3, the greater the content of coarse polypropylene fibers, the more obvious the enhancement effect; the combination of two types of fine fibers and coarse fibers exhibited better performance compared to using a single type of fine fiber and coarse fiber; fine fibers with a smaller aspect ratio showed a better effect on enhancing the shear strength and shear toughness of concrete. The shear strength and axial compressive stress of PFRC were found to follow the Moore-coulomb criterion.