# Micromechanism of the Dispersion Behavior of Polymer-Modified Rejuvenators in Aged Asphalt Material
## 3 Results  
### Gel Permeation Chromatography Analysis  
The molecular weight distribution curves for the samples of aged asphalt binder, virgin asphalt binder, and the corresponding rejuvenated samples (by using CR, MR-1 and MR-2), are presented in Figure 4. Compared with the aged samples, the proportion of smaller molecular weight components increased with different degrees in the D1, D2, and D3 slices. Obviously, the molecular weight distribution changes were caused by the dispersion of rejuvenator with small molecular weight into the aged samples. Therefore, the dispersion capacity and rejuvenated effect of aged asphalt binders can be reflected by the changes degree of GPC curves in D1, D2, and D3 slices. Table 4 shows the calculated correlation coefficients of the GPC curves for different sample depths, and aged sample using a statistical method. Larger correlation coefficients correspond to smaller changes in molecular weight. Table 4 shows that the correlation coefficients of MR-2 was close to that of CR, which mean that the dispersion capacity is similar for MR-2 and CR samples. However, the calculated change in molecular component of MR-1 is significantly smaller than that of MR-2 and CR, which mean that the dispersion capacity of MR-1 is lower than MR-2 and CR. The molecular weight of the rejuvenator's major composition is below 800, and accordingly, the proportion of the molecular weight below 800 (expressed as M800) was used to quantify changes in molecular weight more directly in this study. The mean values of M800 and their standard deviations are shown in Table 5.  
The M800 values for CR in the D1, D2, and D3 slices were 38.8%, 35.0% and 29.8%, respectively. This result indicates that, compared to the aged sample (which has an M800 value of 28.7%), the ratio of substances with a low molecular weight increased, which in turn indicates that the light chemical fractions from the CR rejuvenator diffused into each slice of aged binder to differing degrees. Moreover, the molecular weight distribution of the D2 slice which was rejuvenated by CR is closest to that of the virgin asphalt. The results show that the D2 slice was effectively rejuvenated, and that CR can restore the chemical composition of aged binder to the levels of the virgin binder. Additionally, MR-2 shows a similar effect to CR, with measured M800 values in the D1, D2, and D3 slices of 37.7%, 34.8%, and 29.2%, respectively. This suggests that CR and MR-2 had similar dispersion capacities in the aged asphalt binder. However, the MR-1 rejuvenated sample had significantly lower M800 values in the D2 and D3 slices, which were 29.9% and 29.4%, respectively. The M800 value in the D1 slice is only \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Position**} & \multicolumn{3}{c}{**Correlation Coefficient (r)**} \\ \cline{2-4}  & **CR** & **MR-1** & **MR-2** \\ \hline D1 & 0.969758876 & 0.989985163 & 0.970139281 \\ D2 & 0.988691271 & 0.999302387 & 0.987872939 \\ D3 & 0.999597049 & 0.999829042 & 0.999758177 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Correlation analysis results of GPC curves. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Samples**} & \multicolumn{3}{c}{**CR**} & \multicolumn{3}{c}{**MR-1**} & \multicolumn{3}{c}{**MR-2**} \\ \cline{2-7}  & **Mean Value** & **Standard** & **Mean Value** & **Standard** & **Mean Value** & **Standard** \\  & **of M800** & **Deviation** & **of M800** & **Deviation** & **of M800** & **Deviation** \\ \hline Aged & 28.7 & 1.216 & 28.7 & 1.216 & 28.7 & 1.216 \\ Virgin & 34.1 & 0.925 & 34.1 & 0.925 & 34.1 & 0.925 \\ D1 & 38.8 & 1.053 & 33.7 & 0.931 & 37.7 & 0.832 \\ D2 & 35.0 & 0.921 & 29.9 & 1.823 & 34.8 & 1.056 \\ D3 & 29.8 & 1.336 & 29.4 & 1.521 & 29.2 & 1.228 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Mean values of M800 and their standard deviations of GPC tests. 33.7%, which indicates that its chemical composition was not restored to the level of the virgin binder.