纤维对混凝土裂缝宽度、曲折度及渗透性的影响

为研究不同纤维（钢纤维（SF）、聚丙烯长纤维（Macro-PP）、聚丙烯短纤维（Micro-PP））对荷载作用下带裂缝混凝土渗透性能的影响，通过劈裂试验引入不同宽度的结构裂缝（50~200 μm），比较不同纤维对卸载后混凝土裂缝宽度及曲折度的影响。利用自主研发的渗透装置，分析了不同纤维类型、掺量及混杂方式对荷载作用下不同裂缝宽度混凝土渗透性的影响。研究发现:单掺55 kg/m3 SF比25 kg/m3渗透系数降低95.7%。与单掺SF相比，SF和Macro-PP的掺入具有正混杂效应；Micro-PP与SF混杂体系中渗透系数基本无变化，研究表明Micro-PP对结构裂缝间桥接作用甚微，对渗透性的作用不明显。SF和Macro-PP可有效限制裂缝的扩展，增大表面曲折度，降低开裂后混凝土的渗透性。 

Effect of fiber on the crack width,tortuosity and permeability of concrete

In order to study the effects of different fibers (steel fiber (SF), macro polypropylene fiber (Macro-PP) and micro polypropylene fiber (Micro-PP) on the permeability of fractured concrete under loading, different cracks(50-200 μm) were introduced by splitting test. The effects of different fibers on the crack width and tortuosity after unloading were compared. The influence of different fiber types, dosage and hybrid methods on the permeability of concrete with different crack width under load was analyzed by using the permeability test setup. It is found that the permeability decreases by 95.7%, if the steel fiber content increases from 25 kg/m³ up to 55 kg/m³. Compared with single-doped SF, the hybrid use of SF and macro-PP fibers indicates clear positive composite effect on the permeability; It has little change in permeability of cracked concrete reinforces with SF, micro-PP fiber and the combination of both fibers. The investigation demonstrates that the micro-PP fibers show low effect on restriction of the structural crack and the permeability. Steel fibers and macro-PP fibers restrictes the expansion of cracks effectively, increases the tortuosity of crack surface greatly, and reduces the permeability of cracked concrete greatly.