Ultra High Performance Fiber Reinforced Concrete multi-cracking analysis in different flexural characterization tests

The mechanical characterization of Ultra High Performance Fiber Reinforced Concrete (UHPFRC) still presents certain aspects to delve into, particularly concerning its tensile behavior. European regulations advocate characterizing the material's tensile behavior through three-point bending tests on notched specimens, coupled with back analysis to establish a linearized constitutive law in tension. However, recent literature emphasizes the existence of structural effects in the characterization tests, which require careful consideration. The present paper proposes an experimental investigation on 15 UHPFRC specimens, with a volume fraction of 3.3 % of high carbon steel fibers, with the objective to compare various types of bending tests on slabs and on notched and unnotched beams. This work highlights the intrinsic structural effects of the tests, explaining the mechanical responses of the same material subjected to different types of tests. The goal of this study is to provide enhanced insights, particularly regarding the strain distribution, across various bending test methods. This aims to establish a reliable benchmark for future use in calibrating constitutive relationships and predictive models for UHPFRC bending behavior.