The Study On The Mode I Fracture Character Of Fiber Reinforced Concrete Based On The Double K Model

The cement concrete pavement has a high strength, stiffness and service life, besides, it also has a good plate property. However, the brittle fracture property of cement concrete restricts its use in the high grade pavement construction. While, the use of polypropylene fiber would improve the fracture property of cement concrete pavement which alter its strength and toughness better than before. Nevertheless, despite the Polypropylene Fiber Reinforced Concrete (FRC) has already been developed for nearly 40 years, most studies were still forced on its basic performance including the compression strength, bending strength, frost resistance and impact resistance, and few of scholars tended to research the fracture performance of the FRC. As a result, based on the mode I fracture performance of concrete which is the most frequent damage in pavement this paper studied the fiber reinforced concrete as follows:First of all, this paper utilized the digital speckle correlation method technique to observe the horizontal displacement field and strain field of notched three bending test specimens. Through the analysis of the above two fields, it was found that the fiber would improve the fracture performance of concrete;Besides, based on the double K model, the fracture performance of plain concrete and FRC were analyzed. From the analysis, this paper found that the fiber content had little influence on the initial crack toughness of concrete. On the contrary, the unstable crack toughness was affected greatly by the fiber content with a positive correlation. What's more, the calculated fracture energy were also augmented with the increase of fiber content and the fracture energy of 3.2% fiber volume content concrete would be 30 times bigger than that of plain concrete. Meanwhile, with the increase of fiber content, the three bending test of FRC also appeared an obvious plastic fracture behavior. Furthermore, with the large general FEM software ABAQUS, this paper used the cohesive zone model of concrete fracture mechanics to simulate the three bending test of FRC and took the fracture energy of FRC in the test as the control index of the softening curve in the following calculation. Through the comparison between the simulated P-CMOD curve and the measured results in the test, this paper observed that numerical model could accurately predict the maximum value of load and crack mouth open displacement of specimens. However, the phenomena such as delayed crack and the increased ductility caused by the fiber should be researched in future.