纤维类型对混凝土抗压强度和弯曲韧性的增强效应及变异性的影响

Effect of fiber type on compressive strength and flexural toughness of concrete and analysis of variability

为研究单掺钢纤维、聚丙烯纤维和纤维素纤维对混凝土抗压强度及弯曲韧性的影响,在不同体积掺量下进行了混凝土试块的抗压强度及弯曲韧性试验,并对试验结果进行了变异性分析。试验结果表明:3种纤维混凝土抗压强度较素混凝土平均提高26.7%、6.1%和11.1%;二次抗压强度保持率分别达77.0%、45.7%和58.0%;抗弯承载力最大分别提高31.6%、3.5%和14.0%;基于荷载挠度曲线、Newkumar法及弯拉应力应变曲线分别计算的弯曲韧性指数I_(20)、Newkumar指标PCS_m和韧度比R_x分别为素混凝土的4.2、3.1、2.6倍,19.9、9.8、6.9倍和4.0、3.4、2.7倍。变异性分析结果表明,掺入纤维后混凝土的抗压强度变异性小于弯曲韧性。同时,基于Newkumar法和应力应变曲线法算得的混凝土弯曲韧性指标变异系数小于荷载挠度曲线法。总体而言,钢纤维增强混凝土的抗压强度和弯曲韧性最为显著,且变异系数最小。纤维素纤维增强混凝土抗压强度及聚丙烯纤维增强混凝土弯曲韧性则相对较显著。

This paper aims to study the effect of single-doped steel fiber, monofilament polypropylene fiber and cellulose fiber on compressive strength and flexural toughness of concrete. The compressive strength and flexural toughness of concrete specimens were firstly tested under different volume fraction of fibers, and the variability of test results was then analyzed. The test results show that the compressive strength of the three kinds fiber reinforced concrete are 26.7%, 6.1% and 11.1% higher than that of normal concrete respectively. The average retention tate of secondary compressive strength are 77.0%, 45.7% and 58.0%. The flexural toughness index I 20 , Nemkumar index PCSm, and toughness ratio R x of fiber reinforced concrete are 4.2 times, 3.1 times, 2.6 times, and 19.9 times, 9.8 times, 6.9 times, and 4 times, 3.4 times, 2.7 times higher than of normal concrete respectively, which these based on load-deflection curves, Nemkumar method and bending-tension stress-strain curves, The results of the variability analysis show that the compressive strength of concrete is less than the flexural toughness after the incorporation of fiber. Meanwhile, the coefficient of variation of flexural toughness of concrete obtained from Nemkumar method and bending stress-strain curves is less than that of load-deflection curve method. Overall, the compressive strength and flexural toughness of steel fiber reinforced concrete are the most significant with the smallest coefficient of variation, and the compressive strength of cellulose fiber reinforced concrete and the flexural toughness of polypropylene fiber reinforced concrete are relatively significant.