# Durability Evaluation Study for Crumb Rubber-Asphalt Pavement
## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Asphalt Type** & **Mixing Temperature (\({}^{\circ}\)C)** & **M\({}_{1}\) (g)** & **M\({}_{\text{C}}\) (g)** & **M\({}_{2}\) (g)** & **M\({}_{3}\) (g)** & \(\triangle\)L (\%)** \\ \hline SK-70 & 170 & 505 & 448.9 & 476.3 & 456.6 & 71.9 \\ \hline SBS & 170 & 512 & 455.1 & 491.1 & 472.2 & 52.5 \\ \hline
12\% TPS & 170 & 507 & 450.7 & 481.1 & 469.4 & 38.5 \\ \cline{2-6}  & 185 & 516 & 458.7 & 492.3 & 482.4 & 29.5 \\ \hline
13.5\% TPS & 170 & 520 & 462.2 & 493.6 & 480.8 & 40.8 \\ \cline{2-6}  & 185 & 510 & 453.3 & 485.2 & 475.2 & 31.3 \\ \hline
15\% TPS & 170 & 514 & 456.9 & 491.9 & 476.5 & 44.0 \\ \cline{2-6}  & 185 & 508 & 451.6 & 482.6 & 472.8 & 31.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Test results from the boiling–sieving method. (3) Crumb rubber-asphalt mixture water stability evaluation:  
The splitting strength ratios recorded for the different specimen types within the freeze-thaw-boiling split testes are listed in Table 6, and Table 7 summarizes the results of the Cantabro abrasion test under water-immersion. Table 6 and Figure 7 shows that \(TSR_{1}\) (Unaged and Freeze-Thaw) under the standard test method all meet the technical requirements, and the difference of the rubber particle asphalt mixture with different asphalt types on moisture stability cannot be directly and effectively distinguished. However, \(TSR_{2}\)(Long-term aged and Freeze-Thaw-Boil cycle) of the test method proposed in this study can directly assess that the mixture with SBS-modified asphalt does not meet the technical requirements, and the long-term performance of crumb rubber-asphalt mixture with TPS high-viscosity-modified asphalt is obviously superior to other types. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{3}{*}{**Asphalt Type**} & \multicolumn{2}{c}{**Mixing Temperature (\({}^{\circ}\)C)**} & \multicolumn{2}{c}{**Indirect Tensile Strength Ratio (\%)**} & \multicolumn{2}{c}{**Technical Requirement (\%)**} \\ \cline{3-6}  & **(\({}^{\circ}\)C)** & & & & \\ \cline{3-6}  & **(\({}^{\circ}\)C)** & & & & \\ \hline SK-70 & 170 & 4.3 & 85.6 & 76.3 & \(\
ot\sim\)75 \\ \hline SBS & 170 & 4.2 & 86.9 & 77.4 & \\ \hline
12\% TPS & 185 & 4.5 & 95.6 & 86.3 & \(\
ot\sim\)80 \\ \hline
13.5\% TPS & 185 & 4.2 & 96.8 & 86.5 & \\ \hline
15\% TPS & 185 & 4.6 & 95.8 & 85.7 & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Results of indirect tensile tests under a freeze-thaw–boil cycle [56; 57]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Asphalt Type**} & \multicolumn{2}{c}{**Mixing Temperature (\({}^{\circ}\)C)**} & \multicolumn{2}{c}{**Standard Flying Loss Ratio (\%)**} & \multicolumn{2}{c}{**Water Immersion**} & \multicolumn{2}{c}{**Technical Requirement (\%)**[58]**} \\ \hline SK-70 & 170 & 19.4 & 36.2 & \(\
ot\sim\)20 \\ \hline SBS & 170 & 14.4 & 25.9 & \\ \hline
12\% TPS & 185 & 11.5 & 14.4 & \\ \hline
13.5\% TPS & 185 & 11.0 & 14.8 & \(\
ot\sim\)15 \\ \hline
15\% TPS & 185 & 12.9 & 15.2 & \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Results of Cantabro test under water-immersion. Figure 6: Test results from the boiling–sieving method with different asphalts. Data presented in Table 7 and Figure 8 indicate that the experimental evaluation method proposed in this study is significantly different from the conventional water stability evaluation method. For example, the mixture with SK-70 and SBS modified asphalt can meet the technical requirements under normal test conditions, but it is completely unsatisfactory under water immersion. It is proved that the durability evaluation method proposed in this study can more effectively evaluate the long-term moisture stability of crumb rubber-asphalt pavement. The above-mentioned test results indicate that it is necessary to adopt the moisture stability evaluation system proposed in this study to account for the specific characteristics of crumb rubber-asphalt mixture.