Influence of fibre distribution and orientation on the flexural behaviour of beams cast from flowable hybrid polymer–steel FRC

• Fibre content and orientation were characterized in beams of flowable hybrid polymer–steel FRC.
• Casting under full-scale conditions induced an uneven fibre distribution.
• The tensile behaviour based on standard tests overestimated the behaviour for full-scale beams.
• The tensile behaviour was adjusted to account for variations in fibre content and orientation.

The present study analyses the performance of full-scale beams cast from flowable hybrid polymer FRC with regard to fibre distribution and orientation. To identify possible flow-induced effects, variations of the fibre contents and orientation factors were investigated along the length and over the height of the beams. The study includes a comparison of the fibre distribution and orientation between standard specimens and full-scale beams, and the influence thereof on flexural behaviour and design assumptions. For the full-scale beams, it is found that fibres, even combined, distribute differently by type: steel fibres tend to segregate after a certain flow length, while polymer fibres distribute evenly. Furthermore, polymer fibres seem to adopt a higher degree of preferred orientation, especially in the bottom half of the beams. This research confirms that the modelling of the full-scale beams on the basis of results from standard specimens leads to an overestimation of their flexural response. However, the present study demonstrates how such overestimation can be considerably reduced if the tensile response from standard tests is adjusted to account for variations in the fibre content and orientation.