Dynamic strength and ductility of ultra-high performance concrete with flow-induced fiber alignment

- Ultra-high performance concrete with fiber alignment was tested dynamically.
- Dynamic compressive strength was independent of fiber orientation in the tests.
- Strain at peak stress increased with more fibers perpendicular to the applied load.

The effect of fiber alignment on dynamic strength and ductility of an ultra-high performance concrete has been investigated. A beam was cast to produce a realistic level of flow-induced fiber alignment. Cores were drilled from the beam, and fiber orientation was non-destructively characterized using x-ray computed tomography. Fiber orientations in three orthogonal directions were significantly different at a 95% confidence level, with fibers preferentially aligned in the direction of flow during placement. Cored specimens were then tested in high-strain rate compression using a split-Hopkinson pressure bar. Dynamic compressive strength was independent of fiber orientation for the specimens tested. Ductility, measured by the strain at peak stress, increased with the proportion of fibers oriented perpendicular to the applied load.