## 4 Conclusions  
In this study, SSEA-type epoxy asphalt material was prepared using an SBR/SBS modifier. With BJ200 as the control group, binder performance testing and mixture performance research were carried out, and the main research conclusions are as follows:  
1. With the increase in the proportion of asphalt in the epoxy bitumen, the shear resistance of SSEA gradually decreases, the tensile strength tends to decrease, the elongation gradually increases, low-temperature relaxation capacity tends to increase, and the increase in the asphalt phase accelerates the stress relaxation of the material and reduces the accumulation of stresses.
2. The immersion residual stability and TSR of SSEA mixtures are higher than those of BJ200. SSEA mixtures have excellent water loss resistance and meet the water stability requirements of seamless bridge expansion joints.
3. With the increase in the proportion of asphalt in the epoxy asphalt, the high-temperature performance of SSEA mixtures gradually decreases, and the low-temperature performance gradually increases. High-temperature performance is still better than BJ200 and low-temperature performance is lower than BJ200.
4. Based on the requirements for both high- and low-temperature performance, SSEA-3's comprehensive performance is the best. SSEA-3's high-temperature performance is  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Types of Expansion Joints** & **BJ200** & **SSEA-3** \\ \hline Cost (USD/m) & 385.66 & 358.12 \\ Design service life (years) & 10 & 10 \\ Pavement design life (years) & 20 & 20 \\ Number of replacements & 2 & 2 \\ during pavement life cycle & 41.32 & 38.57 \\ Replacement cost of pavement over its & 1239.62 & 1151.5 \\ service life (USD/m) & \\ \hline \hline \end{tabular}
\end{table}
Table 6: Cost comparison of different seamless expansion joints.  
better than that of BJ200, while its low-temperature performance is slightly lower than that of BJ200.  
The combined results of the above studies show that by comparing the five SSEA mixtures and commercial BJ200, SSEA-3 combines both high- and low-temperature performance and water stability. Currently, the dosage rates of SBR and SBS modifiers are 12% and 2.5%, respectively, and the ratio of epoxy resin, asphalt, and the curing agent is 1:4:1.6, which means its use can be recommended in subtropical regions.  
Although this study presents optimized epoxy asphalt seamless expansion joint materials, there is still room for further exploration. The next step is planned to calculate the thermal stress and relaxation modulus master curves of SSEA-3 mixes in bridge expansion joint structures, and then analyze the fatigue performance of the materials under dynamic loading and temperature changes using finite element simulation and introduce new modifiers such as nanomaterials to enhance the low-temperature crack resistance and durability. Additionally, we plan to investigate these properties by conducting flame-retardant tests to assess fire resistance, as well as permeability tests to evaluate water infiltration resistance and noise reduction performance under typical traffic conditions. In the end, we plan to investigate methods for reusing reclaimed asphalt pavement (RAP) and incorporating recycled materials into the modified epoxy asphalt mixture. This may not only reduce the environmental impact of road construction but also lower the material costs.  
Investigation, X.L. and B.D.; data curation, X.L. and B.D.; funding acquisition, X.L.; writing--original draft, X.L. and B.D.; methodology, Z.M.; writing--review and editing, Z.M. All authors have read and agreed to the published version of the manuscript.  
This work was sponsored by the Major Science and Technology Project of Nanjing (no. 202209012).  
Not applicable.  
All authors have read and agreed to the published version of the manuscript.  
All data, models, and code generated or used during the study appear in the submitted article.  
The authors declare no conflicts of interest.