Testing Study On The Toughness Of Steel Fiber Reinforced Concrete

SFRC is a new construction material. Because of its outstanding mechanics state, simple and convenient construction technology and notable economical benefit, the role of SFRC becomes more and more important in the field of Civil Engineering. In this paper, some studying work is done centering on deformed steel fiber toughening state.Analyzing the using range of the theory of steel fiber reinforcing and toughening mechanics(Composite Material Theory, Fiber Spacing Theory and Interfacial Bond Theory) during the failure course of stress of SFRC. Using these theories, the effect of steel fiber on deformation characteristic and failure law is analyzed when the steel fiber is broken. The result show that steel fiber can improve the toughness of matrix concrete after cracking greatly.Investigating the existent studying achievement of evaluation methods of toughness of steel fiber concrete. The limitations of these methods are summarized and the principle of founding up the evaluation method of toughness index of steel fiber concrete is given. Based on these results and the theory of fracture mechanics set up the new evaluation methodæ¡­racture-CMOD toughness method.The concept of strength and toughness index of steel fiber concrete is founded. In order to use the strength and toughness index for design and apply of SFRC unified theoretical calculation formula of reinforcing and toughening of SFRC is given.Experiments on bending toughness, breaking toughness and cube strength test results are carried out in connection with various kind of deformed steel fiber. Based on these test results, the effect of the kind of fiber on the reinforcing and toughening state of SFRC is analyzed The experimental results show that the kind of fiber affect the reinforcing and toughness state of SFRC greatly.The experimental results are analyzed using Fracture-CMOD toughness method, flexural toughness index IsJioJao and toughness index design value. Comparing the correlation of these three methods with characteristic parameter of steel fiber shows that Fracture-CMOD toughness method is more applicable to compared analysis of toughening state of various kind of SFRC.