## 2 Materials
### Binder Preparation  
Four types of binders were evaluated in this study, including virgin binder, SBR-modified binder, EMAA-modified binder, and EMAA-SBR (compound)-modified binder. The modified asphalt binders were prepared as follows:  
(1) SBR-modified asphalt  
First, the virgin binder was heated up to 155 \(\pm\) 5 \({}^{\circ}\)C. Then, based on the group results [21], the optimum amount of SBR (3% of total binder weight) was added to the virgin binder and stirred for 20 min. After that, the binder was sheared at 5000 r/min for 30 min. During this process, the temperature was kept constant.  
(2) EMAA/SBR compound-modified asphalt  
The virgin binder was heated up to 155 \(\pm\) 5 \({}^{\circ}\)C. Then, a proper amount (1%, 2%, 3%, 4%, 5%, or 6% by total weight) of EMAA was added to the binder and stirred for 30 min. After that, the binder was sheared at 5000 r/min for half an hour. Finally, 3% SBR was added and continuously sheared for another 30 min.  
In this study, the contents of EMAA were preliminary selected as 1%, 2%, 3%, 4%, 5%, and 6% by total weight of the binder specimen. Various important material parameters, including softening point, equivalent softening point, kinematic viscosity, and ductility (10 \({}^{\circ}\)C), in accordance with JTG E 20-2011 [22], were used to determine the optimum dosage of EMAA. The physical properties of modified binders with different EMAA contents are shown in Table 5.  
It can be seen in Table 5 that after adding EMAA, the softening point, equivalent softening point (T800), and kinematic viscosity (135 \({}^{\circ}\)C) of asphalt increased. This indicates that EMAA can improve the high-temperature stability of SBR-modified asphalt. The reason might be that EMAA promoted the stability and compatibility of SBR-modified asphalt, and also the methyl branched chain on EMAA could increase the viscosity of asphalt. However, as the content of EMAA increased from 1% to 6%, the ductility (10 \({}^{\circ}\)C) decreased from above 100 to 76.5 (cm). Thus, the critical point could be at 4% EMAA. Moreover, when the content of EMAA was more than 4%, the increasing rate of softening point,  
Figure 1: Shape and appearance of EMAA and SBR.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Binder Type**} & **Softening Point/\({}^{\circ}\)C** & **Equivalent** & **Kinematic** & **Ductility** \\  & **Point/\({}^{\circ}\)C** & **Softening Point** & **Viscosity** & **(10 \({}^{\circ}\)C)/cm** \\ \hline
3\%SBR & 57.5 & 53.4 & 1.33 & \textgreater{}100 \\
1\% EMAA + 3\% SBS & 65.5 & 56.9 & 1.45 & \textgreater{}100 \\
2\% EMAA + 3\% SBS & 68.9 & 59.3 & 1.58 & \textgreater{}100 \\
3\% EMAA + 3\% SBS & 73.2 & 61.9 & 1.73 & \textgreater{}100 \\
4\% EMAA + 3\% SBS & 74.3 & 63.2 & 1.82 & \textgreater{}100 \\
5\% EMAA + 3\% SBS & 75.0 & 64.3 & 1.89 & 92.3 \\
6\% EMAA + 3\% SBS & 75.5 & 64.8 & 1.93 & 76.5 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Physical properties of EMAA/SBR compound-modified asphalt.  
equivalent softening point (T800), and kinematic viscosity (135 \({}^{\circ}\)C) gradually decreased. For economic considerations, 4% of EMAA was chosen in this study.  
(3) Preparation of EMAA-modified asphalt  
Asphalt with 4% EMAA was also produced. The procedures were the same as mentioned previously.  
Four kinds of binders, including virgin binder, virgin binder + 3% SBR, virgin binder + 4% EMAA + 3% SBR, and virgin binder + 4% EMAA, were recorded as virgin, 3%SBR, 4%EMAA/3%SBR, and 4%EMAA for simplicity.