纤维种类与尺寸对喷射混凝土弯曲韧性的影响

Influence of Fiber Type and Size on Flexural Toughness of Shotcrete

选取不同种类与尺寸的4种型号的纤维,分别以0.7%和1.0%的体积掺量制成混凝土试件进行预切口三点弯曲试验,由混凝土弯曲荷载与跨中挠度的关系曲线计算出纤维喷射混凝土的弯曲韧性指数,进而分析研究纤维种类、几何尺寸及掺量对纤维喷射混凝土弯曲韧性的影响。结果表明:纤维掺量和形状相同时,纤维长度越长混凝土的弯曲韧性提升效果越显著,但纤维长度的确定需考虑对混凝土工作性的影响;对于钢纤维和有机纤维,端部弯钩或表面压痕均可增大纤维与基材之间的黏结力,提高弯曲韧性;与钢纤维相比,有机纤维PP30-55对喷射混凝土弯曲韧性的提升效果更显著,体积掺量1.0%时弯曲韧性指数I5=13.10。

Four types and sizes of fibers were selected to make concrete specimens with fiber content of 0.7% and 1.0% respectively and precut three-point bending tests were carried out.The flexural toughness index of fiber shotcrete was calculated from the relationship curve between bending load and mid span deflection of concrete,and the effects of fiber types,geometrical dimensions and fiber content on the flexural toughness of fiber shotcrete were analyzed and studied.The results show that when the fiber content and shape are the same,the longer the fiber length is,the more significant the effect of improving the flexural toughness of the concrete is,however the influence of the fiber length on the workability of the concrete should be considered when determining the fiber length.For steel fiber and organic fiber,the end hook or surface indentation can increase the cohesive force between the fiber and the base material,which could improve the flexural toughness.The organic fiber PP30-55 has a more significant effect on the improvement of the flexural toughness of shotcrete by comparing with steel fiber,when the fiber volume content is 1.0%,the flexural toughness index I5 is13.10.