Predicting the postcracking strength of ultra-high performance fiber reinforced concrete by means of three-point bending tests according to EN 14651

The postcracking strength of ultra-high performance fiber reinforced concrete (UHPFRC) can be determined directly in axial tensile tests or derived from, for example, bending tests. The latter requires further consideration due to the nonlinear behavior of a UHPFRC specimen in bending. In order to provide a simple but experimentally validated determination of the postcracking strength by means of bending tests, three-point and four-point tests on beams as well as direct tensile tests on specimens sawn out of beams were carried out with different UHPFRC mixtures. The direct tensile tests showed a systematic variation of the postcracking strength within a beam's cross section, which may be attributed to a systematically heterogeneous fiber distribution and orientation. A correlation between the mean postcracking strength of a beam's cross section and the residual flexural tensile strength at small midspan deflection obtained from threepoint test could be established. The proposal will be considered for predicting the postcracking strength according to the forthcoming German guideline on UHPFRC.