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通过劈裂试验和渗透试验,研究了结构型钢纤维、聚丙烯粗纤维和聚丙烯细纤维对开裂后混凝土的裂缝恢复率、劈裂韧性和渗透系数的影响。研究结果表明:钢纤维和聚丙烯粗纤维的掺入可限制裂缝扩展,使混凝土由脆性破坏转为韧性破坏,提高开裂混凝土在卸载后裂缝的恢复作用,显著减小开裂后混凝土的渗透系数。钢纤维掺量越高,裂缝恢复和渗透性降低越明显,钢纤维掺量由25kg/m~3增加至55kg/m3时,渗透系数减小了87%。钢纤维和聚丙烯粗纤维的掺入具有较好的正混杂效应,当裂缝宽度为150μm时卸载,单掺25kg/m~3钢纤维和4kg/m~3聚丙烯粗纤维与单掺35kg/m~3钢纤维相比,渗透系数减小了60%。而聚丙烯细纤维对开裂混凝土的裂缝恢复和渗透性影响较小。
The effects of structural steel fiber, polypropylene crude fiber and polypropylene fine fiber on crack recovery rate, splitting toughness and permeability coefficient of concrete after cracking were studied by splitting test and penetration test. The results show that the incorporation of steel fiber and polypropylene crude fiber can limit the crack propagation, make the concrete transform from brittle failure to ductile failure, and improve the recovery effect of cracked concrete after unloading and significantly reduce the permeability coefficient of concrete after cracking. The higher the content of steel fiber, the more evident the reduction of fracture recovery and permeability. When the steel fiber content increased from 25kg / m ~ 3 to 55kg / m3, the permeability coefficient decreased by 87%. The incorporation of steel fiber and polypropylene crude fiber has a good positive hybrid effect, unloading when the crack width is 150μm, single fiber mixed with 25kg / m ~ 3 steel fiber and 4kg / m ~ 3 polypropylene crude fiber and single mixed 35kg / Compared with m ~ 3 steel fiber, the permeability coefficient decreased by 60%. However, polypropylene fine fibers have little effect on crack recovery and permeability of cracked concrete.