不同钢纤维含量对超高性能混凝土结构的抗弯性能影响研究

Effect of different steel fiber content on flexural behavior of ultra-high performance concrete structures

首先就钢纤维对混凝土的增强机理进行了理论分析,然后通过7 mm和20mm 2种长度的钢纤维搭配出12组不同的钢纤维混凝土试件,借助于四点抗折强度试验对其抗弯性能进行了研究。结果表明:钢纤维混凝土中,钢纤维和混凝土一起承担来自外部的荷载,尤其是混凝土材料抗拉强度低,而钢纤维则正好弥补了这一不足,随着荷载的增大,受拉区混凝土会被拉裂,随后破裂面上的钢纤维代替混凝土材料承受拉力,直至所有钢纤维均被拉出混凝土时,构件会突然被破坏;掺入钢纤维后混凝土的抗折强度和抗弯性能均能得以提升,同时存在使得抗弯承载能力最佳的钢纤维掺量临界点,且该临界点与钢纤维的长径比有关;相比于短纤维,长度较大的钢纤维更有利于提高混凝土的抗折强度和抗弯性能;当钢纤维均为7 mm的短纤维时,最佳钢纤维体积百分率在5.0%左右,而当采用20 mm和7 mm纤维搭配使用时,最佳钢纤维体积百分率约为3.0%,2种情况下所得混凝土抗折强度分别为19.18 MPa和22.61 MPa。

Firstly,the reinforcing mechanism of steel fiber to concrete was analyzed theoretically.Then,12 groups of steel fiber concrete specimens with different lengths of 7 mm and 20 mm were prepared.The flexural properties of steel fiber concrete specimens were studied by means of four-point bending test.The results show that when the steel fiber reinforced concrete flexural structure is subjected to external loads,the concrete in the tension zone will be cracked with the increase of loads,and then the steel fiber on the fracture surface will take the place of the concrete material to bear the tension,until all the steel fibers are pulled out of the concrete,the component will be destroyed suddenly.The flexural strength and flexural performance of concrete can be improved by adding steel fibers.At the same time,there is a critical point of steel fibers content,which makes the flexural load-bearing capacity the best,and the critical point is related to the length-diameter ratio of steel fibers.Compared with short fibers,long fibers have more obvious influence on flexural properties of concrete.When steel fibers are 7 mm short fibers,the optimum volume percentage of steel fibers is about 5.0%,while when 20 mm and 7 mm fibers are used together,the optimum volume percentage of steel fibers is about 3.0%.The flexural strength of concrete is 19.18 MPa and 22.61 MPa respectively.