Abstract
To study the influence of polypropylene fibers with different thicknesses on concrete beams, inclined section shear tests of polypropylene fiber concrete beams were carried out. The cracking load, ultimate load, midspan deflection, reinforcement, and strain of polypropylene fiber concrete beams and conventional reinforced-concrete beams under shear were compared and analyzed. The load-bearing capacity of the rectangular beams was improved significantly by polypropylene fiber addition. Compared with conventional reinforced-concrete beams, the limit shear load of concrete beams with polypropylene fibers and multisize polypropylene concrete beams that were reinforced with three types of fibers increased by 8.67% and 17.07%, respectively. By mixing polypropylene fibers into concrete beams, the initial crack shear force of the beam was improved, the number of cracks was increased and the crack width was reduced, which can increase the beam ductility, inhibit crack formation and increase the strength. The computational formula of the shear ultimate bearing capacity of polypropylene fiber–concrete beams was revised according to composite material theory, and the calculated results were consistent with the test values.
Highlights
Polypropylene fibers can be classified as coarse and fine fibers
The load–midspan deflection curve of the test beams is shown in Fig. 6, and the midspan deflection that corresponds to the ultimate load is shown in Table 4, in which the B0 test team used an A0 specimen, the B1 test team used an A1 specimen and the B2 test team used an A2 specimen as concrete, respectively
The curves of B0 and B1 are basically the same in the middle and later stages of loading analysis, but the multisize polypropylene fiber concrete has a greater strain in the transverse direction. These results show that multisize polypropylene fibers can enhance the plastic deformation capacity of concrete, improve the brittle failure of the beam, and enhance the ultimate shear-bearing capacity of the concrete beam
Summary
Polypropylene fibers can be classified as coarse and fine fibers. Fine polypropylene fibers are relatively small, can refine cracks after being mixed with concrete, improve the original defects of the concrete structure to a certain extent and inhibit cracks. Compared with conventional reinforced-concrete beams, the ultimate shear-bearing capacities of concrete beam B1 mixed with coarse polypropylene fibers and B2 mixed with three fiber types increased by 8.67% and 17.07%, respectively.
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