## 3 Results and Discussion
### Mechanical Properties of Asphalt Mixtures Modified by Diatomite and Crumb Rubber Particles
#### 3.1.3 Moisture Susceptibility  
The specification (JTG F40-2004) stipulated that the asphalt mixture has good water stability when TSR is more than 80%. Table 6 shows the calculation results of the freeze-thaw splitting tests. It can be seen from Table 6 that diatomic and rubber modified asphalt mixtures have good water stability. Comparing different types of modified asphalt mixtures, it can be found that the addition of diatomic and rubber particles will reduce the freeze-thaw splitting strength of the asphalt mixture. It has a negative impact on the water stability of the asphalt mixtures, which may be due to the fact that rubber particles are added into the asphalt mixture as an elastomer. After rotary compaction fabrication, the rubber particles in the asphalt mixture will be in an extruded state, with a certain degree of internal stress. The combination of this internal stress and the expansion force generated by water freezing increases the damage to the asphalt mixture, which will reduce the water stability of the asphalt mixture.  
Comparing the test data of diatomic and rubber particle compound modified asphalt mixture and base asphalt mixture or SBS + diatomic and rubber particle composite modified asphalt mixture and SBS modified asphalt mixture, it can be found that using SBS modified asphalt as binder has better  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Mixture**} & \multicolumn{8}{c}{**Asphal Mixture Types**} \\ \cline{2-10}  & **AC** & **DRAC** & **SAC** & **SDRAC** & **SMA** & **DRSMA** & **SSMA** & **SDRSMA** \\ \hline R\({}_{\text{T1}}\) (MPa) & 0.816 & 0.885 & 1.0867 & 1.228 & 0.857 & 0.894 & 1.187 & 1.216 \\ R\({}_{\text{T2}}\) (MPa) & 0.724 & 0.745 & 1.036 & 1.151 & 0.764 & 0.775 & 1.135 & 1.153 \\ TSR (\%) & 88.7 & 84.2 & 95.3 & 93.7 & 89.2 & 86.7 & 95.6 & 94.8 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Test results of freeze-thaw splitting tests.  
Figure 7: Test results of low-temperature performance of eight kinds of asphalt mixtures: (**a**) \(R_{B}\); (**b**) \(\varepsilon_{B}\); and (**c**) \(S_{B}\).  
water stability in diatomic and rubber particle composite modified asphalt mixture than using matrix asphalt. Plus, the negative impact of rubber particles on water stability is relatively weak when using SBS modified asphalt. SBS modified asphalt mixture has strong cohesiveness and can well limit the damage caused by the internal stress of rubber particles and the frost heave force of water, which will reduce the damage rate of the asphalt mixture.  
By comparing the TSR data of two kinds of graded asphalt mixture, it can be found that the TSR of the asphalt mixtures with skeleton dense gradation is higher than that of the suspension dense asphalt mixture, and the composite modified asphalt mixture of diatomic and rubber particles also has higher TSR and better water stability. This may be due to the higher asphalt aggregate ratio of skeleton dense asphalt mixture with a better binding effect on aggregate and rubber particles, and the porosity is relatively small, which makes it difficult for external water to enter the internal voids of the asphalt mixture and the interface between asphalt and aggregate or rubber particles, thus improving the water stability of asphalt mixture.