Assessment of fibre content and 3D profile in cylindrical SFRC specimens

The inductive method from Torrents et al. (Mater Struct 45(10):1577–1592, 2012, 1 ) is used to assess the fibre content and orientation in steel fibre reinforced concrete. Despite several advantages, the method presents limitations. On one hand, it was conceived for cubic specimens, which complicates its application in existing structures given the difficulty to obtain cubic cores. On the other hand, it only shows the fibre orientation in the three axes perpendicular to the faces of the specimen, being impossible to derive the orientation in other directions with these results. Moreover, it only gives average values without providing any information on the scatter or probabilistic distribution of the fibre orientation—a parameter that may be essential to for design and to explain differences in the behaviour of concretes apparently with the same average fibre distribution. The objective of this paper is to propose an assessment of the fibre content and orientation profile using the inductive method and cylindrical specimens. First, a modification of the method is proposed. Then, new equations are deducted to generalize the test to samples with different shapes and to assess the anisotropy level as well as the directions with the maximum and the minimum fibre contribution. An extensive experimental program and FEM simulations are performed to validate and determine the accuracy of the formulation developed. The results show that the execution of only one additional measurement per specimen is enough to determine the fibre probabilistic profile in all in-plane directions with a high accuracy.