Summary

The inductive method is a robust and simple non-destructive test to assess the content and the distribution of steel fibres in FRC. Despite the advantages in comparison with other methods, further studies are still needed to define the accuracy, the theoretical basis and the equations for the conversion of the inductance into fibre content and distribution. In fact, although the test provides an indirect estimation of the fibre distribution, currently no equation exists for the assessment of the orientation number, which is a valuable parameter for the design of structures. The objective of the present paper is to address this issue. Initially, the theoretical basis for the calculation of the fibre content is provided. Then, alternative equations are deducted for the fibre contribution and for the orientation number. Different experimental programs and finite element numerical simulations are conducted to evaluate the accuracy of the method and to validate the proposals. The results indicate that the equations currently used may lead to errors of up to 24 %. Instead, the formulation proposed here shows errors far below 2.6 %, allowing the prediction of the orientation number in all directions with a high accuracy. This opens up a new field of application for the test and represents an advance towards the characterization and the quality control of SFRC.