## 4 Conclusions  
In this study, silica fume, ultra-fine silica powder, polypropylene fiber, and lightweight coarse aggregate were used to explore the mix design and engineering properties of PC. The Taguchi method was used to evaluate the optimal design parameters of the fiber-reinforced LPC, and the research results showed that it was an effective method. From the results of the range analysis and variance analysis, it can be seen that due to different failure mechanisms, the influencing factors of various mechanical properties were also different. As far as the compressive strength of the LPC was concerned, the size of the lightweight coarse aggregate was the most important factor. As for the flexural strength and splitting tensile strength of the LPC, the fine aggregate content was the most important factor. It is worth noting that the failure of the LPC specimens was mainly caused by the rupture of the lightweight aggregate. The research results also confirmed that the use of suitable materials and the optimal mix proportions were the key factors for improving the mechanical properties of the LPC. Due to the use of silica fume, ultrafine silica powder, and polypropylene fibers, the 28-day compressive strength, 28-day flexural strength, and 28-day split tensile strength of the LPC specimens prepared in this study were 4.80-7.78, 1.19-1.86, and 0.78-1.11 MPa, respectively. On the whole, the mechanical properties of the prepared LPC specimens were better than those of the LPC with a general composition.  
Conceptualization, C.-W.T.; methodology, C.-W.T. and L.-W.E.; software, C.-K.C.; validation, C.-W.T. and C.-K.C.; formal analysis, C.-W.T.; investigation, C.-W.T. and C.-K.C.; resources, C.-W.T.; data curation, C.-W.T. and C.-K.C.; writing--original draft preparation, C.-W.T. and L.-W.E.; writing--review and editing, C.-W.T. and L.-W.E.; visualization, C.-W.T.; supervision, C.-W.T. and C.-K.C.; project administration, C.-W.T.; funding acquisition, C.-W.T. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Ministry of Science and Technology of Taiwan, grant number MOST 105-2221-E-230-002.  
**Institutional Review Board Statement:** Not applicable.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Performance Parameter** & **Initial** & **Test Results** & **Optimal** & **Test Results** \\  & **Combination** & **(MPa)** & **Combination** & **(MPa)** \\ \hline Compressive strength & A\({}_{2}\)B\({}_{2}\)C\({}_{3}\)D\({}_{1}\) & 7.78 & A\({}_{2}\)B\({}_{3}\)C\({}_{3}\)D\({}_{2}\) & 7.82 \\ Elastic modulus & A\({}_{2}\)B\({}_{1}\)C\({}_{2}\)D\({}_{3}\) & 16721 & A\({}_{2}\)B\({}_{3}\)C\({}_{2}\)D\({}_{3}\) & 17315 \\ Flexural strength & A\({}_{2}\)B\({}_{3}\)C\({}_{1}\)D\({}_{2}\) & 1.86 & A\({}_{1}\)B\({}_{3}\)C\({}_{1}\)D\({}_{2}\) & 1.91 \\ Splitting tensile strength & A\({}_{3}\)B\({}_{3}\)C\({}_{2}\)D\({}_{1}\) & 1.11 & A\({}_{3}\)B\({}_{3}\)C\({}_{1}\)D\({}_{1}\) & 1.22 \\ \hline \hline \end{tabular}
\end{table}
Table 15: The results of the validation tests.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.  
**Acknowledgments:** The authors are grateful to the Department of Civil Engineering of National Chung-Hsing University for providing experimental equipment and technical support.  
**Conflicts of Interest:** The authors declare no conflict of interest.