摘要

To improve fiber orientation in ultra-high performance concrete (UHPC), one L-shape device was developed to control the flow of fresh mixture. A smoothed particle hydrodynamics (SPH) method was used to analyze and simulate the motion of steel fibers in UHPC with flow through this L-shape apparatus. SPH simulation indicated that steel fibers tended to rotate to be parallel with local streamlines and most fibers were aligned in the horizontal channel of this L-shape device, inducing an improvement of fiber orientation in hardened specimens. This modification effect of fiber orientation can be a little strengthened with the decreasing height of the horizontal channel. On the other hand, a colorless, transparent and viscous concentrated suspension was obtained by adding super absorbent polymer (SAP) into water for representing fresh UHPC matrix and the visualization of fiber motion was achieved. This visualization approach, coupled with image analysis of steel fibers in hardened UHPC specimens, well verified the SPH numerical simulation results. Therefore, this type of L-shape apparatus provides a potential method to manually improve the steel fiber orientation in UHPC for better mechanical properties.