# Ultra-High-Performance Concrete (UHPC) Piles and Splicing Options
## 7 Recommendation for Future Research  
Ultra-High-Performance Concrete (UHPC) as a pile material is a relatively new innovative material, and the standard guidelines for design and construction are currently at different advanced stages with regulatory institutions in the concrete industry. To provide enough guidelines for the analysis and design of UHPC piles splices, various splice system designs must consider the characteristics of UHPC class materials.  
As driveability during construction is a significant concern with conventional concrete, it is necessary to investigate the driveability of UHPC piles with pile splices. Additionally, the debonding effect of Fiber-Reinforced Polymer (FRP) materials during pile driving and the effects of soil friction on spliced piles need to be investigated. Also, the shear capacity of the UHPC pile splice section is another topic to investigate.  
Several of the splice systems reviewed in this paper have not been tested adequately in the laboratory and the field. Therefore, future experimental work is recommended for those systems.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Type of Splice**} & \multicolumn{2}{c}{**Useful in**} & \multicolumn{2}{c}{**Durability**} & \multirow{2}{*}{**Cost**} & \multirow{2}{*}{**Ref.**} \\  & **Unplanned** & & & & & **Corrosion-** & \\  & **Situation?** & & & & & **Resistant0** & \\ \hline Welded & No & Good & Moderate & Moderate & Low & Low & [15,41,61] \\ Bolted & No & Good & Moderate & Moderate & Moderate & Moderate & [15,71,51] \\ Post-Tensioned & No & Good & Difficult & Difficult & Moderate & High & [14,17,55] \\ Epoxy-bonded dowel & Yes * & Moderate ** & Moderate & Moderate & Moderate ** & Low & [14,53,54] \\ FRP Sheet/jacket & Yes & Good & Low & Moderate & High & Low & [47] \\ NSM FRP & Yes & Good & Moderate & Moderate & High & Low & [48] \\ Mechanical bar couplers & No & Good & Moderate & Low & Moderate & Low & [17,57,58] \\ \hline \hline \end{tabular}  
* Applicable to unplanned situations but cannot develop the required capacity. ** Good only for preplanned situations. *** Durability can be improved using HSSS or FRP bars.  
\end{table}
Table 3: Comparison of applicable UHPC pile splice methods.  
**Author Contributions:** Conceptualization, M.O., S.S.K.D., A.M. and D.G.; methodology, M.O., S.S.K.D., A.M. and D.G.; software, M.O. and S.S.K.D.; formal analysis, M.O., S.S.K.D., A.M. and D.G.; investigation, M.O., S.S.K.D., A.M. and D.G.; resources, M.O., S.S.K.D., A.M. and D.G.; data curation M.O., S.S.K.D. and A.M.; writing--original draft preparation, M.O., S.S.K.D., A.M. and D.G.; writing--review and editing, M.O., S.S.K.D., A.M. and D.G.; visualization, M.O., S.S.K.D. and A.M.; supervision, A.M. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Florida Department of Transportation (FDOT), grant number BED29 977-03.  
This project for which this study was performed is supported by the Florida Department of Transportation (FDOT). The opinions, findings, and conclusions expressed in this publication are those of the author(s) and not necessarily those of the Florida Department of Transportation or the U.S. Department of Transportation.  
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.