## 3 Results and Discussion
### Fiber Distribution  
Figures 9 and 10 show representative sectional images of Mix 1 and Mix 2. Figure 10 corresponds to the section images obtained at the distances of 35 mm and 220 mm from the end near where the placement was taken for Mix 1, and Figure 10 presents the images obtained for Mix 2. The coefficients of fiber dispersion and orientation distribution for each mixture are presented in Figure 11.  
Figure 8: Load-CMOD curves with different mixes: (**a**) Mix 1, (**b**) Mix 2, (**c**) Mix 3, and (**d**) Mix 4. At the section 35 mm away from the end, which is very close to the placing point, the fiber orientation coefficients were not influenced by the amount of WRA and the consequent rheological properties. On the other hand, at the section 220 mm away after considerable flowing, it can be found that the fiber orientation coefficients are much higher than those 35 mm away for each mixture and that Mix 1 presents a higher coefficient compared to Mixes 2-4. Relatively higher orientation coefficients 220 mm away than at 35 mm can be explained by the rotational movement of a fiber immersed in a fluid based on hydrodynamics, as already mentioned. The placing process adopted in fabricating the beam specimens in this study induced a shear flow, as can be seen in Figure 2, forming a parabolic flow velocity profile. This induced gradual rotation of the fibers and the fibers to be aligned to the flow direction. The fiber orientation coefficients obtained 220 mm away were in a range of 0.52-0.57. If the fibers were all aligned to the flow direction after a long flow distance, the coefficient would be equal to 1. However, the interference among fibers that commonly occurs when the volume fraction of fibers (\(V_{f}\)) is concentrated, that is \(V_{f}\geq r_{f}^{2}\), does not allow such an ideal orientation distribution [52]. Here \(r_{f}\) means the aspect ratio of fiber expressed as a ratio of the fiber length to the fiber diameter. Considering the experimental results of viscosity and yield stress according to the amount of WRA, it could be seen that higher viscosity and yield stress provided a higher fiber orientation coefficient. This means that the rheological properties of the mortar may affect the velocity profile and the interaction among fibers. Figure 10: Images of fiber distribution for Mix 2 (**a**) at 35 mm away and (**b**) at 220 mm away. Figure 9: Images of fiber distribution for Mix 1 (**a**) at 35 mm away and (**b**) at 220 mm away. With regard to the fiber dispersion, Mix 1 presented a slightly higher coefficient than the other mixes. When this result is compared with the rheological test results, it is seen that the fiber dispersion is better in a mix with a higher viscosity and yield stress. However, recalling that it is generally accepted that lower viscosity decreases the fiber segregation resistance, it is more reasonable to state that the mixtures considered in this study did not show any meaningful variation in the fiber dispersion in UHPFRC. The absence of noticeable deterioration in the fiber dispersion even with a large amount of WRA is related to UHPFRC retaining high viscosity for all mixtures. The lowest viscosity measured in this study with the largest amount of WRA was 51.1 Pa s, which is dozens of times higher than the viscosity of normal FRC and several times higher than high viscosity self-compacting concrete (SCC) with steel fibers [40; 42]. A much higher amount of cement and a much lower water to cement ratio of UHPFRC induced relatively much higher viscosity even with a large amount of WRA. In addition, unlike the fiber orientation coefficient, there was no difference in the dispersion coefficient between the results 35 mm and 220 mm away. This means that the fiber dispersion did not change according to the flow distance and none of the mixtures caused any sediment or segregation of fibers along the flow.