The Study Of The Effect Of The Aggregate Size And The Steel Fiber’s Length On The Fracture Property Of SFRC

Steel Fiber Reinforced Concrete(SFRC) composed of water, cement, fine aggregates, coarse aggregates and the random-oriented steel fibers is a kind of multiphase and inhomogeneous composite material. Fracture capability is one of the most important mechanical characteristics of SFRC. The study on fracture characteristic of SFRC not only shows a significant function for understanding the material itself, but also plays an important guiding role in studying the structure and performance and setting up scientific method of structural design. In this paper, through experiment method to study the coupling effects of the aggregate size and fiber length of steel fiber reinforced concrete compressive strength, splitting tensile strength, fracture properties and the influence of roughness of area. The main contents are as follows:(1)Based on the compression tests and wedge splitting tests on the one hundred and ninety-two standard cube of concrete specimens in thirty-two groups, the results indicate the C30 concrete and the C60 concrete have a maximum compressive strength and splitting tensile strength when the aggregate sizes are 30 mm and 20 mm respectively. For SFRC,When the matrix strength is same, the coupling effects between the aggregate size and the steel fiber’s length don’t have obvious influence on the compressive strength of SFRC. The splitting tensile strength increases with the increase of fiber length and it has a best reinforcing effect when the steel fiber’s length to the aggregate size ratio is 3.(2)Based on the three-point bending fracture tests on the one hundred and sixty specimens with the dimension of 150mm*150mm*700mm in thirty-two groups, the test results show the C30 concrete and the C60 concrete have a maximum unstable toughness, fracture toughness and fracture energy when the aggregate sizes are 30 mm and 20 mm respectively. Moreover, the coupling effects between the aggregate size and the steel fiber’s length don’t have obvious influence on the unstable toughness of SFRC. The unstable toughness is influenced by the coupling effects between the aggregate size and the steel fiber’s length obviously. The fracture energy is influenced by the steel fiber’s length significantly but it’s affected by the aggregate size mildly. Meanwhile, the fracture energy increases with the increase of fiber length when the aggregate size is uniform.(3) Using matlab to analysis the fractal of the section of matrix concrete and steel fiber reinforced concrete,the maximum size of the steel fiber reinforced concrete is 20 mm and 30 mm, the analysis results show that the variation trend of fracture energy and fractal dimension is almost consistent for matrix concrete and SFRC.