混杂纤维增强超高性能混凝土弯曲韧性

Flexural toughness of hybrid fiber-reinforced ultra-high performance concrete

为研究混杂纤维增强超高性能混凝土(UHPC)的增韧特性,本文通过33个四点弯曲梁试验研究了单掺钢纤维,单掺钢纤维分别与粗聚烯烃纤维、聚乙烯醇纤维、聚酯纤维、玻璃纤维和玄武岩纤维混掺对改善超高性能混凝土梁弯曲韧性的贡献。测定了荷载-挠度全曲线,分析了纤维品种、几何尺寸对梁增韧效果的影响,并对试件断面形态进行了微观电镜扫描。结果表明:与单掺钢纤维相比,混杂纤维超高性能混凝土具有良好的弯曲变形硬化特性,变形后期仍然具有较高的承载力。本文提出的硬化指数可以较好地表征混杂纤维超高性能混凝土硬化特性。本文明确了混杂纤维超高性能混凝土的增韧特性和增韧机理,提出了混杂纤维超高性能混凝土弯曲韧性的评价指标,为实际工程应用提供参考。

A total of 33 four-point bending beam tests were conducted to investigate the contribution of the single addition of steel fiber(SF),SF blended with coarse polyolefin fiber,polyvinyl alcohol fiber,polyester fiber,glass fiber,and basalt fiber to study the toughening characteristics of hybrid fiber-reinforced ultra-high performance concrete(UHPC)and to improve the bending toughness of UHPC beams.The influence of fiber type and geometric size on the toughening effect of the beam was analyzed,and the cross-sectional shape of the specimen was scanned by an electron microscope.Results showed that compared with the single-doped SF,the hybrid fiber UHPC had better bending-deflection hardening properties and retained higher bearing capacity in the late stage of deformation.The hardening index proposed in this study can well characterize the hardening properties of the hybrid fiber UHPC.In this study,the toughening characteristics and mechanism of the hybrid fiber UHPC were clarified,and the evaluation index of the flexural toughness of the hybrid fiber UHPC was proposed.This index can provide a reference for practical engineering applications.