## 5 Conclusions  
In this study, eccentric compression tests of five UHPC-reinforced RC columns and one comparison RC column were designed and carried out. Based on the results of the eccentric compression tests and theoretical analyses, the following main conclusions were drawn:  
1. UHPC reinforcement improved the load carrying capacity and ductility of eccentrically compressed columns; however, their ultimate load carrying capacity gradually decreased as the eccentricity increased. 2. The stress performance of the UHPC-reinforced eccentric compression columns was greatly improved. The ultimate load capacity and ductility coefficient of the UHPC-reinforced specimens increased by 172.30% and 56.24%, respectively, compared with the comparison RC columns under low eccentric compression. 3. The thickness of the UHPC reinforcement layer had a greater effect on the reinforcement effect. When the eccentricity was 50 mm, the ultimate bearing capacity and ductility coefficient of the reinforcement layer thickness of 50 mm were increased by 45.11% and 9.08%, respectively, compared with an eccentricity of 30 mm. 4. When the volume of the UHPC steel fiber dosage was within a suitable range, the steel fiber dosage impacted the reinforcement effect. The ultimate load-carrying capacity and ductility coefficient of the columns with 2% UHPC steel fiber by volume were increased by 8.96% and 2.60%, respectively, compared with the columns with 1% UHPC steel fiber by volume. 5. Based on the limit equilibrium theory and considering the tensile contribution of UHPC, the formula for calculating the ultimate bearing capacity of eccentrically compressed RC columns reinforced with UHPC was provided, and the error of the calculation results is small, which can be used as a reference in the design of reinforcements. 6. Using UHPC both for reinforcement and new construction has many shortcomings. For example, the cost of UHPC raw materials is approximately 10-15 times that of ordinary concrete, resulting in a high cost of material use. The imperfections in the theory of UHPC structural design make it difficult to apply on a large scale in the main structure of a building or a bridge. The roughness of the UHPC interface affects the interfacial adhesion of the base material in the repair and reinforcement, resulting in the detachment of some parts of the interface over a long period when the load is being held. Nevertheless, UHPC still represents a sustainable development of new reinforcement materials. The application of UHPC in the repair and reinforcement of new bridges at home and abroad and existing bridges is an exponentially growing trend. With the deepening of the study of materials and structures, it can be predicted that the development of relevant norms and standards will propel the applications of UHPC. \begin{table}
\begin{tabular}{c c c c} \hline
**Specimen Number** & **Test Value \(N_{u}\) (kN)** & **Calculated Value \(N_{v}\) (kN)** & \(\eta=N_{u}/N_{V}\) \\ \hline Z1 & 2401.40 & 1902.50 & 1.260 \\ Z2-1 & 6539.20 & 6068.30 & 1.080 \\ Z2-2 & 4596.30 & 4167.50 & 1.103 \\ Z2-3 & 2703.90 & 2912.10 & 0.930 \\ Z3 & 2481.50 & 2703.60 & 0.920 \\ Z4 & 3923.70 & 4396.20 & 0.890 \\ Average value & - & - & 1.031 \\ Standard deviation & - & - & 0.32 \\ Coefficient of variation & - & - & 0.31 \\ \hline \end{tabular}
\end{table} 
Table 5: Comparison of test bearing capacity and calculated bearing capacity. **Author Contributions:** Conceptualization, X.L., C.J. and W.L. ; experiment, M.P., W.C. and H.Z. ; resources, X.L., C.J. and W.L. ; writing--original draft preparation, M.P. ; writing--review and editing, M.P. ; supervision, M.P. ; project administration, X.L., C.J. and W.L. All authors have read and agreed to the published version of the manuscript. **Funding:** This study was funded by the Key Research and Development Project of Guangxi, China (No. AB23075093), the Natural Science Foundation of Guangxi, China (No. 2019 GXNSFBA245071), and the Special Project for Science and Technology Bases and Talents of Guangxi, China (No. AD21159010).