Testing Research On Properties Of Flexure And Bond Of Steel Fiber Reinforced High-Strength Concrete

The performances of flexure and bond of steel fiber reinforced high-strength concrete are studied and the suitable calculating methods and formulas are proposed in this dissertation. The main achievements are as follows:1. By the flexural experiment of 51 high-strength concrete and steel fiber reinforced high-strength concrete beams of 150×150×550mm and 51 beams of 100×100×400mm, the effects of the volume fraction and the type of steel fiber on the cracking bending strength, the ultimate bending strength, the failure mode and the crack development of steel fiber reinforced high-strength concrete are discussed. The dimensional effect of the specimens is studied and the coefficient of dimensional conversion is given. The calculating model and the formulas of the bending strength of steel fiber reinforced high-strength concrete are established, which are connected with those of plain concrete.2. Based on the load-deflection curves obtained from the experiment of bending toughness of 68 test beams, the effects of the volume fraction and the type of steel fiber on the bending performance are analyzed. The results of the experiment of bending toughness are compared with those of the experiment of fracture strength in the two aspects of the cracking bending strength and the ultimate bending strength. Furthermore, The flexural toughness indexes and the variation coefficients of load-carrying capability are calculated and discussed, and it is demonstrated that they increase with the increase of the volume fraction of steel fiber.3. The pull-out experiments are tested with two kinds of bond length, namely, the full-length bond of 126 specimens and the local bond of 102 specimens. The concrete block is a cube of 150-mm. The bond stress-slip relation of the free end and that of the loaded end between steel fiber reinforced high-strength concrete and the rebars, such as deformed rebars and smooth rebars, are measured. The whole failure process and the failure mode of bond test of steel fiber high-strength concrete are surveyed. The bond mechanism between deformed rebars and steel fiber reinforced high-strength concrete is discussed and the effects of the volume fraction and the type of steel fiber and the bond length on the ultimate bond strength are analyzed. Besides, the calculating formula of the ultimate bond strength of steel fiber reinforced high-strength concrete is put forward, which is relevant to that of normal concrete.