纤维对混凝土裂缝宽度、曲折度及渗透性的影响
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摘要
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(50～200μm),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55kg/m3 SF比25kg/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MicroPP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。
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(50-200μm)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.
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(50-200μm)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.
引文
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[2]邓宗才.混杂纤维增强超高性能混凝土弯曲韧性与评价方法[J].复合材料学报,2016,33(6):1274-1280.DENG Zongcai. Flexural toughness and characterization method of hybrid fibers reinforced utra-high perforcemance concrete[J].Acta Materiae Compositae Sinica,2016,33(6):1274-1280(in Chinese).
[3]俞家欢,刘琼阳.水泥基复合材料中纤维拉拔的变位约束细观力学模型[J].复合材料学报,2008,25(5):147-150.YU Jiahuan,LIU Qiongyang.Meso-scale variable engagement model for single fiber reinforced concrete under uniaxial tension[J].Acta Materiae Compositae Sinica,2008,25(5):147-150(in Chinese).
[4] DING Y,YOU Z,JALALI S.Hybrid fiber influence on strength and toughness of RC beams[J].Composite Structures,2010,92(9):2083-2089.
[5] DING Y,ZHANG Y,THOMAS A.The investigation on strength and flexural toughness of fibre cocktail reinforced self-compacting high performance concrete[J].Construction and Building Materials,2009,23(1):448-452.
[6] KERMANI A.Permeability of stressed concrete:Steadystate method of measuring permeability of hardened concrete studies in relation to the change in structure of concrete under various shortterm stress levels[J].Building Research and Information,1991,19(6):360-366.
[7]王海龙,张晓龙.压荷载持续作用状态对混凝土中氯离子输运规律的影响[J].水利学报,2015,46(8):974-980.WANG Hailong,ZHANG Xiaolong.Effect of different sustained compressive loads on the chloride transportation in concrete[J].Journal of Hydraulic Engineering,2015,46(8):974-980(in Chinese).
[8] BANTHIA N,BHARGAVA A.Permeability of stressed concrete and role of fiber reinforcement[J].ACI Materials Journal,2007,104(1):70-76.
[9] WANG K,JANSEN D C,SHAH S P,et al.Permeability study of cracked concrete[J]. Cement and Concrete Research,1997,27(3):381-393.
[10] PICANDET V,KHELIDJ A,BASTIAN G.Effect of axial compressive damage on gas permeability of ordinary and highperformance concrete[J].Cement and Concrete Research,2001,31(11):1525-1532.
[11] DESMETRRE C,CHARRON J P.Water permeability of reinforced concrete with and without fiber subjected to static and constant tensile loading[J]. Cement and Concrete Research,2012,42(7):945-952.
[12] YI S T,HYUNT Y,KIM J K.The effects of hydraulic pressure and crack width on water permeability of penetration crack-induced concrete[J].Construction and Building Materials,2011,25(5):2576-2583.
[13] LAWLER J S,ZAMPINI D,SHAH S P.Permeability of cracked hybrid fiber-reinforced mortar under load[J].ACI Materials Journal,2002,99(4):379-385.
[14] WANG K,JANSE D C,SHAH S P,et al.Permeability study of cracked concrete[J]. Cement and Concrete Research,1997,27(3):381-393.
[15]大连理工大学.纤维混凝土试验方法标准[M].北京:中国计划出版社,2010.Dalian University of Technology.Test methods uesd for steel fiber reinforced concrete[M].Beijing:China Planning Press,2010(in Chinese).
[15] ISMAIL M,TOUMI A,FRANCOIS R,et al.Effect of crack opening on the local diffusion of chloride in inert materials[J].Cement and Concrete Research,2004,34(4):711-716.
[16] YI S T,HYUN T Y,KIM J K.The effects of hydraulic pressure and crack width on water permeability of penetration crack-induced concrete[J].Construction and Building Materials,2011,25(5):2576-2583.
[17] NAAMAN A E,NAMUR G G,ALWAN J M,et al.Fiber pullout and bond slip:I—Analytical study[J].Journal of Structural Engineering,1991,117(9):2769-2790.
[18] HUBERT M,DESMETRRE C,CHARRON J P.Influence of fiber content and reinforcement ratio on the water permeability of reinforced concrete[J].Materials and Structures,2015,48(9):2795-2807.
[20] BEAR J.Dynamics of fluids in porous media[M].Milton Keynes:Courier Corporation,2013.