## 3 Results and Discussions
### Influence of Process Parameters on the Emulsification-Separation Effect  
An orthogonal test was used to study the effect of three factors--namely, temperature, time, and speed--on the PL, FMR, and asphalt content of RAP. As shown in Figure 6, with a decrease in temperature, the asphalt content showed an increasing trend, the FMR was also relatively low, the PL showed an increasing trend, and the peak of the PL appeared. Under the condition of same the temperature, with an increase in time and speed, the PL and asphalt content showed a decreasing trend; the FMR gradually increased, indicating that the longer the processing time and the higher the speed, the better the separation effect on RAP and the more asphalt removed. However, the corners of the aggregates were severely abraded as the time and speed increased; so, subsequent experimental conditions must also consider the angularity of the aggregate. Intuitive analysis was used to characterize the influence of different conditions on the emulsification-separation effects and determine the optimal conditions. Tables 3-5 present an intuitive analysis of the asphalt content, FMR, and PL results obtained from the orthogonal test. K\({}_{1}\), K\({}_{2}\), and K\({}_{3}\) represent the average test results obtained when factors were at the same level, and the magnitude of R indicates the degree to which different factors affect the separation effect. In Table 3, the primary and secondary factors affecting the asphalt content were temperature > rotation time > rotation speed. Temperature had the greatest impact on the RAP emulsification-separation effect, while time and rotation speed had similar effects. This is because asphalt is sensitive to temperature and can be softened by heating. In addition, as the temperature increases, the activation energy of the ionic surfactant significantly increases, and it is completely ionized in the solution system, enabling it to react with the asphalt and dissolve it. However, when the temperature is too high, the solution boils easily, the asphalt foam and mineral foam is reduced, and the latter is unlikely to float. Figure 5: Influence of anionic surfactant type and content on oil removal efficiency. Types and contents of surfactants: (**a**) gradation, (**b**) asphalt content and SDBS emulsion/RAP, (**c**) gradation, and (**d**) asphalt content. coarse and fine aggregates before and after emulsification-separation treatment. When the rotation speed and temperature reach a certain level, the fine aggregates can quickly detach from the coarse aggregates, and the coarse and fine emulsification-separation aggregates are basically consistent with the extracted aggregates. Therefore, to improve the FMR, the optimal combination is a rotation speed of 1800 RPM, a temperature of 90 \({}^{\circ}\)C, and a time of 90 min. In Tables 3 and 4, the difference in R values between the asphalt content and FMR is relatively small, indicating that when the asphalt content and FMR decrease or increase, they become less sensitive (to a certain extent) to changes in factor combinations. In Table 5, the order of factors affecting the PL is rotation time \(>\) rotation speed \(>\) temperature. Under the condition of constant speed and temperature, as the processing time extends, the mechanical action gradually causes collisions between aggregates, and more agglomerates are opened up. To reduce agglomeration, the optimal combination is a rotation speed of 1800 RPM, a temperature of 90 \({}^{\circ}\)C, and a time of 90 min. Using gray correlation analysis based on temperature, time, and rotation speed, the correlation of temperature and time with the asphalt content, FMR, and PL was above 0.7, while the correlation with rotation speed was 0.5. In summary, compared to rotation speed, temperature and time had a greater impact on the dispersion effect of RAP. Regarding RAP clusters and separation, the optimal separation parameters for emulsification-separation technology were 80 \({}^{\circ}\)C, 1800 RPM, and 90 min.