A Study On The Fracture Of Reactive Powder Concrete By Wedge Splitting Test

The existence and development of cracks is an important reason for steel corrosion and the reduction of durability of reinforced concrete structures. The toughness and crack resistance of concrete are especially important for engineering structure of reactive powder concrete. The ultra-high strength is often accompanied by high brittleness and the ability of ultra-high strength concrete to avoid catastrophic brittle failure is characterized by high toughness and high energy dissipation capacity. Therefore, how to evaluate the occurrence and development of the cracks in the ultra-high strength concrete structure scientifically and comprehensively is a basic and advanced topic to improve the safety, applicability and viability of the structure and to expand the application of reactive powder concrete.Fracture performance test of reactive powder concrete is carried out by using wedge splitting method in this paper. The P-CMOD curves of the test loading process are measured and the crack initiation loads of each specimen are captured through the strain gauge method. According to the experimental phenomena, the characteristics of crack propagation are analyzed. Variation rules of parameters with initial crack depth ratio and steel fiber content is studied based on measured data. The parameters include initial cracking load, breaking load, initial fracture toughness, fracture toughness, sub-critical expansion length of crack, fracture energy and so on. On this basis, fracture performance of reactive powder concrete and ordinary steel fiber concrete are compared and fracture parameters measured by the wedge splitting method and three point bending method are compared. Through the analysis and calculation of the characteristics reflected in the fracture process zone, the softening curve of the fracture process zone suitable for reactive powder concrete is given. The crack development process of reactive powder concrete flexural members is calculated by using the softening curve and the applicability of the softening curve is verified.The results of this study indicate that when the seam depth ratio of the reactive powder concrete without steel fibre is less than 0.6, the complete P-CMOD curve can not be measured. And the cracking process includes initiation stage and final failure stage. The complete P-CMOD curve can be measured for the reactive powder concrete with steel fibre. And the cracking process includes initiation stage, crack stability expansion stage and unstable failure stage. The influence laws of seam depth ratio on fracture parameters of different steel fiber content are different. The sub-critical expansion length of crack and unstable fracture toughness of reactive powder concrete without steel fibre are not related to the seam depth ratio, which can be used as a stable fracture parameter to evaluate the fracture properties of reactive powder concrete. The fracture toughness, sub-critical expansion length, fracture toughness and fracture energy of reactive powder concrete with steel fibre decrease with the increase of seam depth ratio, which have notch sensitivity. The fracture toughness, sub-critical expansion length, fracture toughness and fracture energy of reactive powder concrete have all been greatly improved by the addition of steel fiber, which enhances the fracture toughness and nonlinear characteristics of reactive powder concrete. Compared with that measured by three point bending method, the unstable fracture toughness measured by wedge splitting method is larger. Compared with ordinary steel fiber reinforced concrete, the fracture toughness of reactive powder concrete is better. Virtual crack stress distribution of reactive powder concrete can be well reflected by Petersson formula softening curve, which is obtained through the test data. The expressions of the softening constitutive law are derived, which can reflect the influence of the seam depth ratio. The results of numerical analysis show that the softening curve can well simulate the crack development process of reactive powder concrete structure.