纤维对开裂后混凝土渗透性及裂缝恢复的影响
Effect of fibers on permeability and crack relaxation of cracked concrete

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25 kg/m3增加至55 kg/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150 μm时卸载，单掺25 kg/m3钢纤维和4 kg/m3聚丙烯粗纤维与单掺35 kg/m3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。 Splitting test and water permeability test were conducted. The effect of steel fiber, macro polypropylene fiber and micro polypropylene fiber were evaluated on crack relaxation ratio, splitting test toughness and permeability coefficients of cracked concrete. The results show that the addition of steel fiber and macro polypropylene fiber restrains crack propagation and improves toughness of concrete. They aid in converting the brittle failure of concrete into ductile failure. The crack relaxation increased with the use of steel fiber and macro polypropylene fiber. The permeability coefficients also decrease. The crack relaxation and impermeability increase with the increasing of steel fiber dosage. The permeability of concrete decreases by 87%, with steel fiber content increasing from 25 kg/m3 to 55 kg/m3. The hybrid use of steel fiber and macro polypropylene fiber shows significant positive hybrid effect. When unloading at crack width of 150 μm, the permeability of concrete reinforced by 25 kg/m3 steel fiber and 4 kg/m3 macro polypropylene fiber decreases by 60%, compared to that reinforced by 35 kg/m3 steel fiber. Micro polypropylene fiber has little effect on crack relaxation and permeability of cracked concrete. 国家自然科学基金（51578109）