Fracture properties of steel fiber reinforced concrete: Size effect study via mesoscale modelling approach

Steel fiber reinforced concrete (SFRC) can exhibit superior performances of high strength and toughness due to the enhancing effect of discontinuous steel fibers randomly distributed in concrete matrix. For better understanding the size effect on the fracture properties of SFRC structural elements, we developed a three-dimensional (3D) two-phase mesoscale model considering the random distribution and orientation of steel fibers in concrete, to investigate the quasi-static flexural responses of the notched SFRC beams with different beam depths, i.e., 30 mm, 60 mm, 90 mm, 120 mm and 150 mm. A new coupling method was employed to describe the interfacial relationship between steel fibers and concrete matrix in the present simulations. The fracture behaviors of SFRC beam were numerically studied in terms of the load versus cracking mouth opening displacement curve, the evolution of fracture process zone, the nominal flexural strength and the fracture failure patterns. Through the analysis and comparison between the present numerical results and the available test data, it was found that there is negligible size effect on the fracture patterns of SFRC beam. The size effect on the nominal flexural strength of SFRC beam can be well characterized and analyzed using the Baz?ant's size effect law. Further, the numerical results of SFRC beams showed a favorable agreement with the corresponding test results, demonstrating the great feasibility and potential of the developed mesoscale modelling approach in simulating and investigating the mechanical behaviors of SFRC.