## Materials and Methods  
### Materials  
In this paper, base bitumen AH-90 was used as the binder. According to the Chinese national standard (JTGE40-2004) [45], AH-90 is bitumen with penetration between 80 and 100. The penetration, softening point, ductility, Brookfield viscosity and density of bitumen were determined according to the Standard Test Methods of Bitumen and Bituminous Mixtures for Highway Engineering (JTG E20-2011) [46]. The physical indexes of the base bitumen are listed in Table 1.  
The basalt fiber was used in this paper to modified asphalt mixture. The appearance is shown in Figure 1. The basic technical properties are listed in Table 2. From previous study of our research group on basalt fiber modified asphalt mixture [47], the basalt fiber also has the low hydrophilicity, high heat resistance and high oil absorption (oil absorption rate is 6.154%). Basalt fiber provides a feasibility for the application of composite modified asphalt.  
\begin{table}
\begin{tabular}{c c c} \hline
**Property** & **Test Results** & **Standard Requirements** \\ \hline Penetration (25 \({}^{\circ}\)C, 5 s, 0.1 mm) & 85.8 & 80–100 \\ Softening point T\({}_{R\&B}\) (\({}^{\circ}\)C) & 46.9 & \(\geq\)45 \\ Ductility (25 \({}^{\circ}\)C, cm) & \textgreater{}150 & \(\geq\)100 \\ Brookfield viscosity (135 \({}^{\circ}\)C, Pa-s) & 306.9 & — \\ Density (15 \({}^{\circ}\)C, g/cm\({}^{3}\)) & 1.016 & — \\ \hline \end{tabular}
\end{table}
Table 1: Basic properties of bitumen.  
Figure 1: Appearance of basalt fiber.  
Nano-materials are white color, made by chemical methods and inorganic synthetic materials. The molecular formula is TiO\({}_{2}\)/CaCO\({}_{3}\), and the appearance is shown in Figure 2. It is soluble in water. The supporting particles are rod-shaped and the outer titanium dioxide particles are flake-shaped (diameter is 50-60 nm), with regular structure and excellent covering power.  
The coarse and fine aggregates used in the test were sieved, and the physical properties of coarse aggregates, fine aggregates and mineral powders were tested according to the requirements of JTG E42-2005 [49]. The results are shown in Tables 3-5.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Property** & **Test Results** & **Standard Requirements**[48] \\ \hline Diameter (\(\mu\)m) & 10–13 & — \\ Length (mm) & 6 & — \\ Moisture content (\%) & 0.030 & \(\leq\)0.2 \\ Combustible content (\%) & 0.56 & — \\ Linear density (Tex) & 2398 & 2400 \(\pm\) 120 \\ Fracture strength (N/Tex) & 0.55 & \(\geq\)0.40 \\ Tensile strength (MPa) & 2320 & \(\geq\)2000 \\ Tensile modulus of elasticity (GPa) & 86.3 & \(\geq\)85 \\ Elongation at break (\%) & 2.84 & \(\geq\)2.5 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Technical properties of basalt fiber.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Granular** & **Apparent** & **Saturated Surface—Dry** & **Bulk Specific** & **Water Absorption** \\
**Grade (mm)** & **Specific Gravity** & **Bulk Specific Gravity** & **Gravity** & **Rate (\%)** \\ \hline
13.2 & 3.142 & 3.066 & 3.031 & 1.17 \\
9.5 & 2.992 & 2.943 & 2.917 & 0.86 \\
4.75 & 3.084 & 3.001 & 2.961 & 1.35 \\
2.36 & 2.721 & 2.646 & 2.603 & 1.67 \\
1.18 & 2.661 & 2.602 & 2.566 & 1.38 \\
0.6 & 2.758 & 2.709 & 2.681 & 1.07 \\
0.3 & 2.684 & 2.635 & 2.606 & 1.13 \\
0.15 & 2.907 & 2.82 & 2.776 & 2.14 \\
0.075 & 2.627 & 2.528 & 2.476 & 2.04 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Physical properties of aggregate.  
Figure 2: Images of nano TiO\({}_{2}\)/CaCO\({}_{3}\) materials: (**a**) appearance; (**b**) SEM images (5000\(\times\)).