超高分子量聚乙烯纤维混凝土静态力学性能研究

Research on the Static Mechanical Properties of Ultra-high Molecular Weight Polyethylene Fiber Reinforced Concrete

纤维混凝土较普通混凝土具有更加优异的阻裂、增强和增韧效果,能更好地满足现代混凝土工程设施的要求。作者以高强、高弹模、低密度的捻制超高分子量聚乙烯(UHMWPE)纤维作为增强体,试验研究一种新型纤维混凝土的准静态力学性能。通过改进制备流程,研制C70等级的4种纤维体积掺量纤维混凝土,通过劈裂抗拉、立方体抗压和棱柱体轴心压缩试验,研究纤维掺量对混凝土强度和变形性能的影响。最后,试验结果与未处理UHMWPE纤维混凝土及聚丙烯纤维混凝土进行对比。结果表明:改进的制备工艺提高了纤维在混凝土中的分散均匀性,改善了混凝土的和易性;纤维使混凝土试件破坏时保持了良好的整体性,避免了大量碎块的脱落;UHMWPE纤维显著提高了混凝土劈裂抗拉强度,当纤维掺量为0.3%~1.0%时,强度提高率为47.2%~78.6%;纤维对混凝土单轴抗压强度作用不明显,但极大改善了残余抗压强度;压缩峰值应变及泊松比随纤维掺量增加而增大,弹性模量则相反,压缩韧性指数ηc15.5为素混凝土的1.40倍~2.53倍;捻制UHMWPE纤维较其他两种纤维更加显著地改善了混凝土的劈裂抗拉强度,并对单轴抗压强度有一定的增强效果。

Fibre reinforced concrete,which possesses more excellent properties of cracking resistance,reinforcing strength and toughness than plain concrete,can fulfill more requirements in the modern concrete constructions. In the current paper,the twisted ultra-high molecular weight polyethylene( UHMWPE) fibre of high strength,high elastic modulus as well as low density was employed as the reinforcement,the quasi-static mechanical properties of a new type of fibre concrete( FRC) were experimentally investigated. The C70 high strength concretes with four different fiber volume fractions( FVF) were developed by improving the process of preparation,then the splitting tensile tests,cubic uniaxial compression tests as well as the prism axial compression tests of the FRC were conducted,respectively,to investigate the effect of FVF on quasi-static strengths and deformation behaviour of the FRC. The comparisons between the mechanical properties of current studied UHMWPE FRC and concrete reinforced by general UHMWPE fibre without treatment as well as the Polypropylene fibre were performed. The results showed that the fibre dispersed more evenly using this improved mixing method which promoted the workability of FRC. The integrity of concrete was maintained and fall-out of fragments was avoided due to the added UHMWPE fibre. The splitting tensile strength,increasing from 47. 2% to 78. 6% with the fiber content from 0. 3% to 1. 0% compared with the plain concrete,was significantly improved by the twisted UHMWPE fibre. However,the compressive strength of the concrete was not significantly enhanced by the UHMWPE fibre,while the improvement of the residual compressive strength was remarkable. Both the peak compressive strain and Poisson's ratio increased with the increase of the FVF,whereas the elastic modulus had an opposite variation trend. The compressive toughness index ηc15. 5of FRC was 1. 40 ~ 2. 53 times of that of the plain concrete. Twisted UHMWPE fibre improved the splitting tensile strength of concrete more significantly than the other two types of fibres,and enhanced the uniaxial compressive strength to a certain degree.