Influences of Steel Fiber Content on Size Effect of the Fracture Energy of High-Strength Concrete

Quasi-brittleness is an important factor affecting the size effect of concrete, and the addition of steel fiber can effectively change this effect in concrete. The size effect on the fracture energy of steel fiber reinforced high-strength concrete was investigated in this paper. A total of 156 concrete single-edge notched beams (SENB) of various span-to-depth ratios, crack-to-depth ratios and steel fiber contents were tested to study the size effect of fracture energy of the high-strength concrete added steel fibers. The parameters of fracture in the boundary effect model (BEM) and size effect law (SEL) were deeply analyzed. The results show that the addition of steel fiber will generate significant influence on the parameter values obtained from both BEM and SEL. Based on the BEM, the relationship among G(f) (experimental test fracture energy), g(f) (local fracture energy), and G(F) (fracture energy unaffected by specimen boundary) could be obtained. Thus, a method for analyzing the influence of steel fiber on G(F) was proposed using small-size SENB specimens at laboratory. In addition, based on the SEL, the impact of size effect on the fracture energy was effectively mitigated by the addition of steel fibers in high-strength concrete to a certain extent.