## 3 Results and Discussion
### Low-Temperature Performance  
Prior research on asphalt properties showed that the low-temperature performance of emulsified asphalt is weakened at varying degrees by WER systems [19]. Other studies also revealed that WER-EA mixtures are more prone to temperature shrinkage cracks in cold environments, which reduce the bearing capacity of asphalt pavements and ultimately lead to various problems in the pavements. In this study, a low-temperature indirect tensile test at \(-10\)\({}^{\circ}\)C was conducted to explore the influence of different epoxy values on the low-temperature properties of WER-EA mixtures and design a scheme to reduce the negative impact of the WER system on the low-temperature properties of the mixtures. The relevant indexes of splitting tensile strength (\(R_{T}\)), failure tensile strain (\(\varepsilon_{T}\)), and failure stiffness modulus (\(S_{T}\)) were calculated as follows:  
\[R_{T}=0.006287P_{T}/h \tag{6}\]  
\[\varepsilon_{T}=X_{T}\times\left(0.0307+0.0836\mu\right)/\left(1.35+5\mu\right) \tag{7}\]  
\[S_{T}=P_{T}\times\left(0.27+1.0\mu\right)/\left(h\times X_{T}\right) \tag{8}\]  
Figure 8: Dynamic stability results of asphalt mixtures. \[X_{T}=Y_{T}\times\left(0.135+0.5\mu\right)/\left(1.794-0.0314\mu\right) \tag{9}\]  
where \(R_{T}\) represents the splitting tensile strength (MPa); \(P_{T}\) stands for the maximum load value of the test (N); \(\varepsilon_{T}\) represents the destruction of tensile strain; \(S_{T}\) indicates the modulus of breaking stiffness (MPa); \(h\) stands for the height of the specimen (mm); \(\mu\) indicates the Poisson ratio, which took a value of 0.25 in this study; and \(X_{T},Y_{T}\) are the total horizontal and vertical deformation, respectively, of the specimen corresponding to the maximum test load (mm). The relevant indexes of splitting tensile strength (\(R_{T}\)) for the four WER-EA mixture samples are shown in Figure 9. Although the current regulations in China do not limit the \(R_{T}\) value exactly, a higher \(R_{T}\) value is used to characterize the superior low-temperature stress bearing capacity of an asphalt mixture. Figure 9 shows that the cleavage strength of the E20-T mixture was 0.37 MPa, 0.15 MPa, and 0.26 MPa lower than that of the EA mixture, respectively, indicating that the low-temperature performance of the WER-EA mixtures was worse than that before modification. The \(R_{T}\) value of the E20-T mixture was the smallest, but the difference between the \(R_{T}\) value of the E51-T mixture and that of the E51-T mixture was small, and the splitting strength of the E44-T mixture was 12.36% higher than that of the E20-T mixture. It can be seen that the use of E44 was beneficial for the asphalt mixture in withstanding higher-temperature stress before low-temperature cracking. Figure 10 shows the \(\varepsilon_{T}\) test results for each asphalt mixture. It was found that the tensile strain of the three WER-EA mixtures was significantly reduced compared to the blank control group. The \(\varepsilon_{T}\) value difference between the E44-T and E51-T mixtures was small, but the \(\varepsilon_{T}\) value difference between the E20-T and E44-T mixtures reached 17.68%, indicating that the E20-T mixture had more room for improvement in resistance to low-temperature cracking. The \(\varepsilon_{T}\) value of the E44-T mixture was larger, indicating that its shrinkage deformation ability was less affected by the low temperature, and its low-temperature cracking resistance was stronger. Figure 11 shows the \(S_{T}\) values for the four mixtures. It can be seen from the figure that the three WER-EA mixtures had a larger stiffness modulus. The \(S_{T(\text{E44-T})}\) was smaller than the \(S_{T(\text{E20-T})}\) and the \(S_{T(\text{E51-T})}\), but the \(S_{T(\text{E44-T})}\) and \(S_{T(\text{E51-T})}\) were only 70 MPa, 16.07% lower than the \(S_{T(\text{E20-T})}\). The E20-T mixtures had the highest \(S_{T}\) value, i.e., they were more brittle and had the worst low-temperature properties.