# Laboratory Evaluation of Rejuvenating Agent on Reclaimed SBS Modified Asphalt Pavement
## 3 Results and Analyses
### Phase Characteristics of Rejuvenating Agents on Aged Modified Asphalt  
Polymer SBS in asphalt absorbs light oil to form the polymer phase. Under the fluorescence excitation, the polymer phase reflects longer wavelength light, appearing white. In contrast, the asphalt phase does not reflect any light, appearing black. So the asphalt phase and polymer phase are clearly distinguished by fluorescence microscope. As the reflected light field is applied, there is no damage to the polymer phase distribution in the asphalt. Hence, the fluorescence microscope gets highly reproducible asphalt micrographs. By analyzing the morphological structure and dispersion state of polymer SBS in asphalt, it is possible to effectively evaluate the role of rejuvenating agent on the aged modified asphalt, and establish the relationship between macroscopic mechanical properties and microscopic characteristics of modified asphalt blends. To ensure the reliability of fluorescence images and avoid the particularity of individual samples, three slides were made in parallel for each sample. Four representative fluorescence images were taken for each slide. Table 8 shows the fluorescent micrographs of aged modified asphalt and modified asphalt blends with different types and proportions of rejuvenating agents. Table 8 shows that the polymer SBS in aged modified asphalt are spherical particles distributed in the asphalt, and this modified asphalt belongs to a single-phase continuous structure, with polymer SBS as dispersed phase and asphalt phase as continuous phase. Compared with modified asphalt blended with different types and proportions of rejuvenating agents, recycling did not change its phase structure, still belonging to single-phase continuous structure. The SBS particle's uniformity is satisfactory. With the naked eye only, one cannot see the difference of SBS particle in appearance and shape. The images have to be further processed to quantify potential differences. Professional image processing software (Image-Pro Plus) is applied to analyze and process the fluorescence images of modified asphalt blends, which can segment, count and measure the images. The area ratio of polymer SBS particles is the quantitative evaluation indexes to describe the phase characteristics and recycling mechanism of modified asphalt. Here the area ratio refers to the percentage of polymer SBS particles area to total area, indirectly reflecting the SBS swelling degree in the asphalt. Table 9 shows the phase characteristics of modified asphalt blended with different proportions of rejuvenating agents. From Table 9, the area ratio of polymer SBS particles increases at first and then decreases, presumably because the proportion of rejuvenating agent was small, and the swelling effect of SBS particles continued with the action of light oil. With the increasing of the proportion of rejuvenating agent, the swelling effect reaches a certain extent, and excess of rejuvenating agent decreases the relative content of SBS particles in asphalt, resulting in the area ratio of SBS particles beginning to decrease. \begin{table}
\begin{tabular}{l c c c c c c c c c c} \hline \hline
**Indexes** & **Aged Modified Asphal** & \multicolumn{6}{c}{**Types of Modified Asphal Blends**} \\ \cline{3-11}  & & **3\%H** & **6\%H** & **9\%H** & **3\%S** & **6\%S** & **9\%S** & **3\%G** & **6\%G** & **9\%G** \\ \hline Area ratio of SBS particles/\% & 2.753 & 3.679 & 2.980 & 2.030 & 3.832 & 3.672 & 3.147 & 4.207 & 4.539 & 4.081 \\ Standard deviation/\% & 0.38 & 0.51 & 0.29 & 0.31 & 0.54 & 0.57 & 0.48 & 0.46 & 0.59 & 0.32 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Phase characteristics of modified asphalt blends.