## 3 Results and Discussion
### SEM Results of the Reinforcements and Interfaces  
In Figure 6a, it can be observed that the nano-CaCO\({}_{3}\) whiskers has a spindle shape, and the crystal shape is large in the middle and small at both ends. The particle size is 10-100 nm, and the aspect ratio is 3-4, which is basically ellipsoidal. As shown in Figure 6b, the CaCO\({}_{3}\) whiskers have elongated needle shapes. The whiskers selected in the test are hexagonal prisms. If considering the cross-section as approximately circular, the whisker diameters are between 1 \(\upmu\)m and 3 \(\upmu\)m. At the same time, it can be observed that the whisker lengths are different. The longest whisker can reach more than 100 \(\upmu\)m, and the shortest one is only a few microns. The length-diameter ratio of whiskers is 15-60. It can be observed from Figure 6c that aramid fibers are bundled and arranged relatively tightly, and the surface is relatively smooth with few adhering substances.  
Figure 5: Multiple Stress Creep Recovery (MSCR) curves of modified asphalt binders and base asphalt binder at **(a)** 0.1 kPa, **(b)** 3.2 kPa.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Asphal**} & \multicolumn{4}{c}{**0.1 kPa**} & \multicolumn{4}{c}{**3.2 kPa**} \\ \cline{2-10}  & **R/\%** & **Error \%** & \
\begin{tabular}{c} Jnr/ \\ kPa-1 \\ \end{tabular} & **Error \%** & **R/\%** & **Error \%** &
\begin{tabular}{c} Jnr/ \\ kPa-1 \\ \end{tabular} & **Error \%** \\ \hline Nano-CaCO\({}_{3}\)-modified asphalt & 1.15 & 5.2 & 0.92 & 11.8 & 0.05 & 7.3 & 1.03 & 10.8 \\ \hline CaCO\({}_{3}\) whisker-modified asphalt & 2.08 & 3.6 & 0.93 & 12.6 & 0.03 & 6.7 & 1.06 & 13.9 \\ \hline Aramid-modified asphalt & 14.34 & 4.3 & 0.88 & 14.7 & 0.65 & 5.9 & 1.69 & 8.4 \\ \hline Base asphalt & 0.93 & 5.1 & 0.93 & 9.8 & 0.02 & 6.4 & 1.03 & 7.2 \\ \hline \hline \end{tabular}
\end{table}
Table 5: The calculation results of recovery rate (R) and average unrecoverable creep compliance (Jnr).  
It can be seen in Figure 7 that nano-CaCO\({}_{3}\) particles are not dispersed into asphalt as individual particles, and the cohesive particles are relatively obvious. The lumps formed after cohesion are more evenly distributed in the asphalt. As shown in Figure 8, the CaCO\({}_{3}\) whiskers are not uniformly dispersed in the asphalt, and there is a phenomenon of agglomeration. Even under vigorous stirring, the CaCO\({}_{3}\) whiskers were not sufficiently dispersed in the asphalt, and did not exert the reinforcing effect of the fibers. The reason may be that the density of CaCO\({}_{3}\) whiskers and asphalt is very different, and CaCO\({}_{3}\) whiskers are precipitated. As shown in Figure 9, the aramid fibers interlaced in the asphalt are spanning the crack and exerting the pull-and-blocking effect.  
Figure 6: Scanning electron microscopy (SEM) results of nano-CaCO\({}_{3}\), CaCO\({}_{3}\) whiskers, and aramid fibers (**a**) nano-CaCO\({}_{3}\), magnification: 20,000\(\times\), (**b**) CaCO\({}_{3}\) whiskers, magnification: 15,000\(\times\), (**c**) aramid fibers, magnification: 2500\(\times\).  
Figure 7: SEM result of nano-CaCO\({}_{3}\)-modified asphalt (magnification: 1000\(\times\)).