基于钢纤维与聚丙烯纤维喷射混凝土的弯曲韧性

Flexural Toughness of Shotcrete Based on Steel Fiber and Polypropylene Fiber

选用4种不同形状和几何尺寸的钢纤维与聚丙烯纤维,分别以体积分数0.7%和1.0%掺入混凝土制成混凝土试件并开展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弯曲韧性指数,继而对比探讨纤维喷射混凝土的弯曲韧性提升效果。结果表明:纤维形状相同时,同等掺量下的混凝土的弯曲韧性与纤维长度呈正相关,但需要兼顾纤维长度对混凝土工作性的影响;纤维与基体间的附着力可通过纤维端部弯钩或表面压痕的方式增强;几何尺寸相同时,聚丙烯纤维比钢纤维的喷射混凝土增韧效果更佳,体积分数为1.0%时弯曲韧性指数为13.10。

Four kinds of steel fibers and polypropylene fibers with different shapes and geometric dimensions are selected,and concrete specimens are made with 0.7%and 1.0%volume fraction respectively,and pre cut three-point bending tests are carried out.The bending toughness index is calculated from the relationship curve between concrete bending load and mid span deflection,and then the effect of improving the bending toughness of fiber shotcrete is compared and discussed.The results show that when the fiber shape is the same,the flexural toughness of concrete with the same content is positively related to the fiber length,but the influence of fiber length on the workability of concrete should be taken into account,the adhesion between the fiber and the matrix can be enhanced by means of hooks at the end of the fiber or surface indentation.When the geometric dimensions are the same,polypropylene fiber has better toughening effect than steel fiber shotcrete,and the bending toughness index is 13.10 when the volume fraction is 1.0%.