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

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