Abstract: In order to explore the effect of straw fiber on the mechanical properties of concrete, this paper researched the mechanical properties of concrete with different lengths of rape straw and fiber volume content of rapeseed under the condition that the water-cement ratio was 0.50 and the strength grade was C35. The influence of rape straw fiber on the mechanical properties of concrete was analyzed by measuring the compressive, splitting, tensile strength and flexural strength of the concrete, and the results were verified by scanning electron microscopy. The results showed that with the increase of the length and the volume content of the rape straw fiber, the compressive strength, splitting tensile strength and flexural strength first increased and then decreased. When the fiber length was 30～40 mm and the volume content was 0.1%, the compressive strength was 47.43 MPa, which was 16.45% higher than that of the control group. When the fiber length was 20～30 mm and the volume content was 0.2%, the splitting tensile and flexural strength of the concrete was 9.1 MPa and 3.71 MPa that were higher than those of the control group. Concrete internal structure with 0.2% and 0.4% fiber volume content was observed by scanning electron microscopy. It was confirmed that there was no large-area porosity at the fiber-concrete interface of 0.2% concrete, and the cement slurry on the fiber. The body was evenly distributed, and a good adsorption and adhesion force and mechanical meshing force were formed with the concrete. The internal fibers of the concrete were filled with harmful pores, no fiber agglomeration, which reduced the stress concentration and enhances the mechanical properties of the concrete.

Key words: rape straw fiber, concrete, mechanical properties, electron microscopy

摘要： 为了探索秸秆纤维对混凝土力学性能的影响机理，研究了在水灰比为0.50、强度等级为C35条件下，不同油菜秸秆纤维长度和油菜秸秆体积掺量的混凝土力学性能。通过测试混凝土的抗压、劈裂抗拉、抗折强度，分析油菜秸秆纤维对混凝土力学性能的影响规律，并使用扫描电镜验证分析结果。结果表明：混凝土的抗压、劈裂抗拉、抗折强度随着油菜秸秆纤维长度的增加和掺量的提高均呈现先增大后减小的趋势；当纤维长度30~40 mm，体积掺量0.1%时，抗压强度为47.43 MPa，比对照组提高16.45%，当纤维长度20~30 mm，体积掺量0.2%时，混凝土的劈裂抗拉和抗折强度为3.71 MPa、9.1 MPa，比对照组提高9.12%、6.64%，扫描电镜对比观察0.2%和0.4%纤维体积掺量的混凝土内部结构，证实0.2%掺量混凝土的纤维-混凝土交界面无大面积孔隙，纤维上水泥浆体均匀分布，与混凝土间形成良好的吸附黏结力与机械啮合力，混凝土内部纤维填充了有害孔隙，无纤维结团现象，减少了应力集中，增强了混凝土的力学性能。

关键词: 油菜秸秆纤维, 混凝土, 力学性能, 电镜扫描