Abstract: Tests of steel fiber pulled out from cement matrix were carried out by self-made mould and the pull out load-displacement curve of common concrete and silica fume reinforced steel fiber concrete are achieved. The content of steel fiber was 0～1.2% by volume fraction and the content of silica fume is 0～12% by quality replacement of cement. The micro-hardness and micro-morphology of the interface between steel fiber-cement matrixes are obtained by micro-hardness test and SEM test. Based on the above experiments, the concept of interface bond pull out toughness was put forward, and the interfacial bond strength and toughness of steel fiber pulled out from cement matrix were calculated and the law of silica fume's impact on the interfacial bond strength, steel fiber pull out toughness, micro-hardness and microstructure of the interface were analyzed. The results of tests show that the interfacial bond strength of steel fiber-cement matrix in steel fiber reinforced concrete is increased by 10.7%～44.2% with the content of 3%～12% silica fumes. The micro-hardness of the interface region is increased by 7.4%～38.8%，and the distance 60 μm, in ordinary concrete, between the weakest layer of the interface and the surface of the steel fiber is reduced to 40 nm after the addition of 12% silica fume, and the greater addition of silica fume, the better effect is shown. With the different additions of silica fume, the displacement of steel fiber under peak loads at time of being pulling out is reduced by 4.1%～25.9%. As for steel fiber reinforced concrete with different content of fiber, the ideal content of silica fume is 6%～9% for the steel fiber's pull out roughness.

Key words: highway engineering, steel fiber reinforced concrete, silica fume, pull out toughness, interfacial bond strength, micro-hardness

摘要： 通过自制模具实现了对钢纤维从水泥石基体中拔出的实验测试，得到基体混凝土中钢纤维体积掺量为0～1.2%、硅灰取代水泥质量掺量为0～12%时钢纤维拉拔荷载-位移曲线图，通过显微硬度和SEM试验，测试得到了钢纤维-水泥石界面纤维硬度及界面区微观形貌特征。在测试基础上，提出了界面黏结拉拔韧性概念，并计算得到了界面黏结强度和拉拔韧性，分析了硅灰对界面黏结强度、拉拔韧性、界面显微硬度和微观形貌特征的影响规律。研究结果表明，硅灰改善了钢纤维-水泥石界面黏结性能，使界面黏结强度提高了10.7%～44.2%；界面区显微硬度提高了7.4%～38.8%，界面最薄弱层与钢纤维表面的距离由普通混凝土的60μm缩小到40μm，且硅灰掺量越大，效果越好；硅灰使钢纤维拉拔时峰值荷载对应的位移下降了4.1%～25.9%；对于不同掺量的钢纤维混凝土，钢纤维拔出韧性的最佳硅灰掺量为6%～9%。

关键词: 道路工程, 钢纤维混凝土, 硅灰, 拉拔韧性, 界面黏结强度, 显微硬度