# Preparation and Properties of SBS/REOB-Modified Rejuvenated Asphalt
## 4 Results and Analysis
### Rheological Test of Low-Temperature Bending Beam  
Previous studies have shown that REOB can achieve a good regeneration effect on aging asphalt, but its crack resistance at low temperature needs to be further improved. Therefore, multiple comparison groups were added to the rheological tests of low-temperature bending beams to better analyze the low-temperature performance of the SBS/REOB-modified and rejuvenated asphalt. The rheological test of a low-temperature bending beam was carried out using an asphalt binder after short-term aging of TFOT (Thin Film Oven Test) and long-term aging of PAV (Pressure Aging Vessel). The test results are shown in Table 10 and Figure 6.  
The higher the brittleness of the asphalt was, the higher the stiffness modulus \(S\) value was, and the low-temperature crack resistance of the material was relatively poor. In contrast, the lower the \(S\) value was, the better the toughness of the material was, the better its low-temperature performance was. For the creep rate in the low-temperature rheological test of the \(m\) value representation of the asphalt trabecular \(S\) value rate, the smaller \(m\) value showed a small asphalt cement \(S\) value rate. Having a certain resistance shows that, under the condition of low temperature, the stress relaxation ability in the actual pavement application environment and the offset of the temperature shrinkage stress gradient ability was stronger, and it had better low-temperature performance [14; 15]. The bar chart of the BBR test results of the PAV aged asphalt at different temperatures from Table 10 is shown in Figure 6.  
From the overall change rule of the \(S\) value and \(m\) value in each figure, the asphalt performance decreased with the decrease in temperature. This is because in a certain range, the content of viscous components in asphalt is positively correlated with the low-temperature performance of asphalt. The decrease in temperature makes the elastic component dominant in asphalt. If the proportion of the viscous component is small, the asphalt hardens and becomes brittle, which makes the asphalt more prone to cracking. From Figure 6a,c,e, the following can be seen from the \(S\) value results of each material at different temperatures: (1) The \(S\) value of 1 the base asphalt and 2 the 9% REOB was significantly higher than that of the modification of 3-7--the rejuvenated asphalt, and the lower the temperature, the more obvious the gap; Figure 6b,d,f show that the \(m\) value was significantly lower than the modified rejuvenated asphalt, indicating that the modified rejuvenated asphalt was better than the rejuvenated asphalt. The low-temperature performance was greatly improved and was better than that of the base asphalt. (2) At \(-12\)\({}^{\circ}\)C, the 9% REOB exceeded the limit range of the creep stiffness modulus. Compared with the matrix asphalt, the low-temperature performance of the 9% REOB was worse. (3) At \(-12\)\({}^{\circ}\)C, except for 9% REOB, all other asphalts met the requirements of \(S\) < 300 MPa and \(m\) > 0.3 specified by SHRP; at \(-18\)\({}^{\circ}\)C, the \(S\) and \(m\) values of matrix asphalt and 9% REOB exceeded this requirement, the \(S\) value of 3.5% SBS + 9% REOB with low SBS content no longer met the requirement, and the rest of the modified rejuvenated asphalt did meet the requirement; at \(-24\)\({}^{\circ}\)C, only 4.5% SBS + 9% REOB met this requirement, while 3 4.5% SBS + 7% REOB only had the \(S\) value within the range, the \(S\) values of the rest of the asphalt were more than 300 MPa, and the \(m\) values were all lower than 0.3. This shows that the modified rejuvenated asphalt had good resistance to low-temperature deformation. (4) The REOB content was controlled to remain unchanged at 9%. Within the range of SBS content 3.5-4.5%, the higher the content, the better the low-temperature performance of the modified rejuvenated asphalt.