为研究多尺寸聚丙烯纤维混凝土的抗弯韧性,采用四点弯曲试验对30个长×宽×高为400 mm×100 mm×100 mm的聚丙烯纤维混凝土试件进行研究,得到纤维混凝土梁的荷载-挠度曲线.基于美国ASTM-C1399-98方法,研究不同尺寸聚丙烯纤维及其混杂纤维对混凝土抗弯韧性的影响.研究结果表明:在相同掺量条件下,直径越小、长度越短的聚丙烯细纤维对混凝土裂前抗弯韧性改善效果越好;聚丙烯粗纤维和多尺寸聚丙烯纤维对混凝土裂后抗弯韧性有较大改善,并且在裂后出现低应力应变硬化现象;在相同掺量条件下,多尺寸聚丙烯纤维对混凝土的抗弯韧性改善效果最好;相对于素混凝土剩余强度,单掺聚丙烯细纤维混凝土剩余强度提高1.53~2.53倍,单掺聚丙烯粗纤维混凝土提高5.58~8.88倍,多尺寸聚丙烯纤维混凝土提高7.76~10.82倍.%In order to study the flexural toughness for multi-scale polypropylene fiber reinforced concrete, thirty 400 mm×100 mm×100 mm polypropylene fiber reinforced concrete beams were investigated by using the four point bending test, and their stress-strain curves were obtained. Based on the ASTM-C1399-98 method and the optimal engineering fiber content, the effects of multi-scale polypropylene fiber and hybrid fiber on the flexural toughness of concrete were studied. The results show that under the condition of the same content, the addition of polypropylene fine fibers will greatly improve the flexural toughness of concrete before cracking. Both coarse polypropylene fiber and multi-scale polypropylene fiber will greatly improve the flexural toughness of concrete, and after cracking a stress-strain hardening phenomenon appears under low stress circumstance. Multi-scale polypropylene fiber reinforced concrete would improve the flexural toughness to the maximum. Compared with the common concrete, the residual strength of fine polypropylene fiber concrete increases by 1.53-2.53 times. The residual strength of coarse polypropylene fiber concrete increases to 5.58-8.88 times. The residual strength of hybrid polypropylene fiber concrete increases by 7.76~10.82 times.
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