Experimental Study on Uniaxial Tensile Properties of Hybrid Fiber UHPC
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摘要: 为探索混杂纤维增强超高性能混凝土(UHPC)的单轴拉伸特性，开展了狗骨形UHPC的轴向拉伸试验，研究了混杂纤维品种和掺率等对UHPC轴拉全曲线、力学指标、断裂能和韧性比等影响规律.采用拉伸韧性比评价混杂纤维UHPC拉伸韧性，并利用扫描电镜(SEM)分析其拉伸破坏机理.研究结果表明：钢纤维与非金属纤维混掺较单掺钢纤维更有利于提高UHPC抗拉强度、峰值拉应变，其增幅分别为4.64%~39.32%和26.98%~65.35%；混杂纤维可充分发挥其协同传荷阻裂和耗能增韧的作用，提高了UHPC的拉伸韧性比和断裂能，混掺玻璃纤维、聚烯烃纤维对提高拉伸韧性比最显著，比单掺钢纤维分别提高15.0%和12.5%；掺入等掺率非金属纤维对断裂能的提高幅度均高于钢纤维，其中混掺玄武岩、玻璃纤维或者聚烯烃纤维对提升断裂能较为明显.基于轴拉试验，给出单掺钢纤维、钢-PVA混杂UHPC指数型应力-裂缝宽度(σ-ω)关系式，理论曲线与试验曲线总体趋势吻合良好，为数值模拟与工程应用提供了参考.Abstract: To explore the uniaxial tensile properties of hybrid fiber-reinforced ultra-high performance concrete (UHPC),the effects of fiber type and fiber volume fraction on the axial tensile curve,mechanical indexes,fracture energy,and toughness ratio of UHPC were studied through the axial tensile test of dog-bone shaped specimen.The tensile toughness ratio was used to evaluate the tensile toughness.The tensile damage mechanism of hybrid fiber UHPC was analyzed by using the scanning electron microscope (SEM).The results show that:steel fiber combined with non-metallic fibers is more conducive than steel fiber only in improving the tensile strength and peak tensile strain of UHPC,and the increase is 4.64%~39.32% and 26.98%~65.35%,respectively;hybrid fibers can give full play to their synergistic load-bearing,crack-blocking and energy-consuming toughening effects,improving the tensile toughness ratio and fracture energy of UHPC.Steel fiber combined with glass fiber or polyolefin fiber has the most significant effect on improving the tensile toughness ratio,which is 15.0% and 12.5% higher than steel fiber only,respectively;at equal volume fraction,the increase in fracture energy of non-metallic fibers are higher than that of steel fiber,in which,basalt,glass fiber or polyolefin fiber have significant improvement in fracture energy.Based on the axial tensile test,the stress-crack width (σ-ω) relationship between single-doped steel fibers and steel-PVA blended UHPC exponentially was given,and the theoretical curves were in good agreement with the test curves,providing a reference for numerical simulation and engineering application.
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