# Silane Modification of Crumb Rubber on the Rheological Properties of Rubberized Asphalt
## 3. Experimental Result and Discussion
### Low Temperature Performance  
The mechanical and deformation behavior of asphalt at low temperature is closely related to its composition. Without any modified materials, matrix asphalt often shows more deflection and brittleness, while rubber powder can greatly improve this situation [23]. The BBR test results are shown in Table 6.  
According to Table 6, the low temperature performance of AM was worse than that of rubberized asphalt. When the test temperature was \(-12\)\({}^{\circ}\)C, the \(S\) and \(m\)-values of AM were 126.5 and 0.347, respectively. At this time, the \(S\) of AR and MAR was 98.4 and 91.1, respectively, while the \(m\)-value of AR was 18.7% higher than that of AM, and the \(m\)-value of MAR was 30.8% and 10.2% higher than that of AM and AR, respectively. The above results indicate that rubber powder improved the low temperature performance of asphalt, produced less low temperature deflection deformation, and enhanced the abilities of stress transmission and internal stress dissipation of rubber asphalt, however, MCR had a better improvement effect. According to Chinese specifications, \(S\) should not exceed 300 MPa and \(m\)-value should not be less than 0.3. It can be seen from the table that when the temperature continued to drop to \(-24\)\({}^{\circ}\)C, the low temperature performance of asphalt sample further declined, and the \(S\) of AM sharply rose to 683.5, which is 123% higher than MAR. Although the \(S\) of AR and MAR were both higher than 300 MPa, their low temperature performances were obviously better than that of AM. Meanwhile, the \(m\)-value of AM was lower than 0.3, and its ability to dissipate  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Index** & **Temperature (\({}^{\circ}\)C)** & **AM** & **AR** & **MAR** \\ \hline \multirow{2}{*}{\(S\) (MPa)} & \(-24\) & 683.5 & 352.7 & 306.2 \\  & \(-12\) & 126.5 & 98.4 & 91.1 \\ \hline \multirow{2}{*}{\(m\) (-)} & \(-24\) & 0.239 & 0.306 & 0.32 \\  & \(-12\) & 0.347 & 0.412 & 0.454 \\ \hline \end{tabular}
\end{table}
Table 6: BBR tests results.  
internal stress was significantly reduced, while rubber asphalt was still higher than 0.3, and MCR gave asphalt a better stress and force transfer effect at a lower temperature.  
The main reasons for this can be concluded as follows. Under the same load level, AM tends to transform the stress into larger bending deformation due to the insufficient level of stress dissipation, and its surface is prone to cracking and brittle fracture. The addition of rubber powder improves the mechanical and force transfer behavior of asphalt. Most of the load is absorbed by rubber powder, so its \(S\) is smaller and \(m\)-value is larger [24]. At the same time and a lower temperature, due to the better combination of MCR and asphalt caused by chemical action, on the one hand, the movement of the asphalt molecular chain is relatively reduced, on the other hand, the friction between MCR and asphalt is enhanced, which builds a better dissipation of the internal stress state. Therefore, MAR has a better low temperature performance.