## 6 Conclusions  
Based on the current infrared spectrum testing technology of SBS asphalt-modifier content, this paper studies the influence of physical and reactive additives on the test accuracy of SBS modifier content, reveals the micro mechanism of the influence of additives on the test of SBS modifier content, and improves the existing sample preparation technology and model algorithm. The main conclusions are as follows:  
(1) The influence of different types of additives on the test accuracy of SBS modifier content was analyzed mainly in this study. The addition of a physical additive has no effect on the test accuracy of the SBS modifier content, but the reactive additive will cause a chemical reaction inside the SBS-modified asphalt, which shows that the addition of reactive additives has a greater influence on the test accuracy of SBS modifier content. (2) The traditional FTIR test-sample preparation method was improved in this study, and the dissolution method was proposed. Compared with the tablet-pressing method, the dissolution method has improved in safety, convenience, applicability, and accuracy, which can be used as an upgrade and improvement of sample preparation technology in infrared spectrum testing. (3) Compared with other studies in this field, this research proposes a new algorithm. Based on the 699 cm\({}^{-1}\) characteristic peak, it can simplify the boundary conditions of sample preparation. There is no need to add additives when preparing standard samples, which greatly improves the application convenience of the test technology. \begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Additive** & **Test Sample** & \begin{tabular}{c} **SBS Modifier** \\ **Content** \\ \end{tabular} & \begin{tabular}{c} **A699/(A699 + A1377)** \\ \end{tabular} & \begin{tabular}{c} **Additive** \\ **Content** \\ \end{tabular} & \begin{tabular}{c} **Test Results** \\ **Content** \\ \end{tabular} & \
\begin{tabular}{c} **Actual SBS** \\ **Content** \\ \end{tabular} &
\begin{tabular}{c} **Error** \\ \end{tabular} \\ \hline \multirow{6}{*}{1} & First group & 4\% & 0.078445 & 2.7\% & 3.82\% & 3.89\% & \(-0.07\%\) \\ \cline{2-7}  & Second group & 4\% & 0.040649 & 2.7\% & 3.88\% & 3.89\% & \(-0.01\%\) \\ \cline{2-7}  & Third group & 4\% & 0.079000 & 2.7\% & 3.94\% & 3.89\% & \(+0.05\%\) \\ \cline{2-7}  & Fourth group & 4\% & 0.042350 & 2.7\% & 3.999\% & 3.89\% & \(+0.10\%\) \\ \hline \multirow{6}{*}{2} & First group & 4\% & 0.082884 & 0.2\% & 3.95\% & 3.99\% & \(-0.04\%\) \\ \cline{2-7}  & Second group & 4\% & 0.042930 & 0.2\% & 4\% & 3.99\% & \(+0.01\%\) \\ \cline{2-7}  & Third group & 4\% & 0.082771 & 0.2\% & 4.07\% & 3.99\% & \(+0.08\%\) \\ \cline{2-7}  & Fourth group & 4\% & 0.044032 & 0.2\% & 4.09\% & 3.99\% & \(+0.10\%\) \\ \hline \multirow{6}{*}{3} & First group & 4\% & 0.076733 & 3\% & 3.79\% & 3.88\% & \(-0.03\%\) \\ \cline{2-7}  & Second group & 4\% & 0.039168 & 3\% & 3.81\% & 3.88\% & \(-0.07\%\) \\ \cline{2-7}  & Third group & 4\% & 0.080241 & 3\% & 3.98\% & 3.88\% & \(+0.10\%\) \\ \cline{2-7}  & Fourth group & 4\% & 0.038898 & 3\% & 3.81\% & 3.88\% & \(-0.07\%\) \\ \hline \multirow{6}{*}{4} & First group & 4\% & 0.081738 & 0.25\% & 3.91\% & 3.99\% & \(-0.08\%\) \\ \cline{2-7}  & Second group & 4\% & 0.040732 & 0.25\% & 3.89\% & 3.99\% & \(-0.10\%\) \\ \cline{2-7}  & Third group & 4\% & 0.083214 & 0.25\% & 4.09\% & 3.99\% & \(+0.10\%\) \\ \cline{2-7}  & Fourth group & 4\% & 0.040900 & 0.25\% & 3.92\% & 3.99\% & \(-0.07\%\) \\ \hline \end{tabular}
\end{table} 
Table 10: Test results of SBS-modified asphalt with additives. **Author Contributions:** Conceptualization, methodology, K.Z. ([PERSON]) and K.Z. ([PERSON]): formal analysis, H.X. ; investigation, G.L. ; resources, K.Z. ([PERSON]) and K.Z. ([PERSON]); writing--original draft preparation, M.S. and H.X. ; writing--review and editing, K.Z. ([PERSON]), H.X., M.S., G.L., K.Z. ([PERSON]); supervision, M.S. All authors have read and agreed to the published version of the manuscript.