## 3 Tests and Results
### The Evaluation of the Thermal Stability and Aging Resistance for Modified Asphalt
#### 3.1.2 Aging Resistance  
Asphalt will be aging during the process of storage, mixing, transportation, construction, and service. Due to the long-time contact with air, under the influence of natural conditions, a series of physical and chemical reactions will happen, which will adversely affect the performance of asphalt pavement. The short-term aging of asphalt is mainly caused by the mixing and paving process. There are two test methods for indoor tests to simulate short-term aging: the thin film oven test (TFOT), and the rolling thin film oven test (RTFOT). (1) Thin Film Oven Test (TFOT) test  
The short-term aging test using the thin film oven test (TFOT) was employed in this paper. The stainless steel discs (diameter 140 mm \(\times\) deep 9.5 mm) were loaded into the ventilation oven. The temperature of the oven was kept at 163 \({}^{\circ}\)C and the speed was kept at 5.5 r/min. After 5 h, the weight loss, penetration ratio, and rutting factor [31] of the aged asphalt samples were determined. The changes of indicators for nano-CaCO\({}_{3}\)/BRA and SBR/BRA compound-modified asphalt after the thin film oven test (TFOT) aging are shown in Table 6.  
From Table 6, it can be observed that the quality of the five modified asphalts has been lost, and the quality loss of the 10% nano-CaCO\({}_{3}\)/BRA compound-modified asphalt is the least compared to that of the BRA. It shows that, during the aging process, the nano-CaCO\({}_{3}\)/BRA compound-modified asphalt has relatively less volatilization. The penetration ratio of 5% SBR/BRA compound-modified asphalt is the largest compared to that of BRA, even reaching 95.5%. This indicates that the 5% SBR can significantly improve the anti-aging properties of BRA. The rutting resistance of the five modified asphalt samples after the thin film oven aging test was compared with rutting resistance before aging. The test data are shown in Figure 5. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Test Items** & **BRA** & **BRA + 3\% SBR** & **BRA + 5\% SBR** & **BRA + 5\%** & **BRA + 10\%** \\  & & & & & **Nano-CaCO\({}_{3}\)** & **Nano-CaCO\({}_{3}\)** \\ \hline Mass loss (\%) & 0.343 & 0.279 & 0.260 & 0.254 & 0.229 \\ Penetration (25 \({}^{\circ}\)C, 0.1 mm) & 26.3 & 24.0 & 22.4 & 24.2 & 22.7 \\ Penetration of after TFOT & 18.8 & 22.5 & 21.4 & 21.2 & 20.4 \\ aging (0.1 mm) & 70.7 & 93.8 & 95.5 & 87.6 & 89.9 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: The changes of indicators for nano-CaCO\({}_{3}\)/BRA and SBR/BRA compound-modified asphalt after thin film oven test (TFOT) aging. Figure 5: The relationship between Nano-CaCO\({}_{3}\)/BRA and SBR/BRA compound-modified asphalt in before and after thin film oven test (TFOT) aging anti-rutting factors (\(G^{*}\)/sin\(\delta\)) and temperature. The results can be observed from the curve change in Figure 5. It is known that both the original anti rutting factor and the anti-rutting factor after thin film oven test (TFOT) aging, the nano-CaCO\({}_{3}\)/BRA, and SBR/BRA compound-modified asphalt are all larger than the BRA. This shows that the addition of SBR and nano-CaCO\({}_{3}\) can improve the anti-rutting performance of BRA. From Figures 6 and 7, it can be observed that at \(-6\)\({}^{\circ}\)C, the stiffness \(S\) and \(m\) value before and after pressure aging vessel (PAV) aging of nano-CaCO\({}_{3}\)/BRA and SBR/BRA compound-modified asphalt with different contents are satisfied with the requirements of \(S\leq 300\) MPa and \(m\geq 0.3\). Under the conditions of \(-6\)\({}^{\circ}\)C and \(-12\)\({}^{\circ}\)C, the \(S\) value of the 5% SBR compound-modified asphalt is the smallest relative to the other four kinds of modified asphalt before and after the pressure aging vessel (PAV) aging, but the \(m\) value is the largest, compared with the other four kinds of modified asphalt. This indicates that the 5% SBR/BRA compound-modified asphalt has the better low-temperature performance.