Luong test to evaluate residual shear behavior of FRC

The behavior of concrete subjected to shear is a complex phenomenon; difficult to be evaluated experimentally. The characterization of the behavior of fiber reinforced concrete (FRC) under shear is even more complex since high displacements are required to assess the post-cracking residual shear response. Such high displacements might produce a change in the test setup, thus inducing bending moments that compromise the reliability of the results. The Luong test - originally proposed to assess shear in plain concrete and rocks - might be a suitable testing method for this purpose. However, no application of this test to FRC is found in the literature. The objective of this study is to propose a simple shear test and adapt it for FRC. For that, an experimental program of Luong test was performed on FRC mixes including steel and macro-synthetic fibers in different contents. Moreover, two variables related to the test setup were analyzed: the height of the specimen and the diameter of the circumferential notch. The results indicate that the Luong test meets the requirements to be applied to the characterization of the shear residual response of FRC in terms of sensitivity of the test and reliability.