# Influence of Different Fibers on Performance of Bitumen Binders and Thin-Overlay Bitumen Mixtures
## 3 Results and Discussion
### Performance Analysis of Fiber Bitumen Mortar  
#### 3.2.1 High-Temperature Rheological Property  
The impact of fiber type and content on the high-temperature performance of SBS bitumen was examined using the DSR test. The findings from this test are depicted in Figure 4.  
As the test temperature escalated from 58 \({}^{\circ}\)C to 76 \({}^{\circ}\)C, the G*/sin\(\delta\) ratio for SBS bitumen mortar plummeted by an astonishing 80.89%. When the fiber content was bumped up to 2%, the G*/sin\(\delta\) for various fiber-reinforced bitumen blends dropped by an average of 79.75%. And if the fiber content was doubled to 4%, the G*/sin\(\delta\) of different fiber bitumen decreased by 76.85% on average. Despite the varying degrees of decrease, all bitumen types exhibited a downward trajectory. The rationale lies in the fact that as the bitumen is heated, the internal molecular friction diminishes, thereby enhancing the bitumen's fluidity.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Fiber Type** & \(m_{\star}\)**/g** & \(m_{\gamma}\)**/g** & \(m\)**/g** & \(p\) \\ \hline Basalt fiber & 165.91 & 175.305 & & 0.879 \\ Polypropylene fiber & 168.025 & 200.14 & 5 & 5.423 \\ Glass fiber & 165.93 & 182.495 & & 2.313 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Test results of fiber oil absorption rate.  
Different fibers have different effects on improving the high-temperature performance of bitumen due to the difference in oil absorption rate and dispersion. When the fiber content is 2%, the improvement effect of polypropylene fiber and glass fiber is better. When the content of is 4%, the \(G^{\star}\)/\(\sin\!\delta\) of both increases, but the improvement effect of polypropylene fiber is better. What plays a leading role is the dispersion of the fiber. The fiber with good dispersion can ensure that the fiber surface is in full contact with the bitumen and increase the oil absorption area. The fiber distribution is more disordered, and the stability of the three-bit network structure is better.  
With the increase in fiber content, the high-temperature performance of bitumen is significantly improved. With the increase in fiber content, the \(G^{\star}\)/\(\sin\!\delta\) of bitumen increases step by step. For instance, consider the rutting factor measured at 76 \({}^{\circ}\)C. At a fiber content of 2%, the average increase in \(G^{\star}\)/\(\sin\!\delta\) hovers around 52.58%. When the fiber content is boosted to 4%, this average rise jumps to approximately 107.04%. This suggests that incorporating fiber enhances the anti-rutting properties of bitumen mortar. Two reasons can explain this observation. First, after the fiber is incorporated, the light components in the bitumen are adsorbed. The content of free bitumen in the mortar system is reduced, and the viscosity of SBS bitumen is improved. Secondly, the random distribution of fibers in bitumen forms a three-dimensional network structure, which produces internal friction resistance in bitumen. The movement of light components is limited, and the transformation of matrix structure of bitumen mortar from sol type to sol-gel type is promoted [57; 58]. Increasing the fiber content can amplify these benefits, leading to even greater enhancement of the high-temperature performance and a reduction in the temperature sensitivity of the bitumen mortar. The anti-rutting performance of fiber-reinforced bitumen is improved.