# Experimental Evaluation of the Durability of Concrete Repair Materials
## 4 Conclusions  
In this study, compressive and flexural strength tests were conducted while considering the strength and physical aspects of the structure, inactive cracks with different widths, and epoxy, impregnant, and epoxy/impregnant repair methods. Moreover, the durability with respect to carbonation, chloride attack, and freeze-thaw was evaluated. The following conclusions can be made:  
1. Repairs that included epoxy exhibited the highest compressive strength. Specimens repaired using epoxy and epoxy/impregnant were approximately 2-5% stronger than those repaired using impregnant. This is because the epoxy filled the cracks with high adhesion. The flexural strength showed a similar trend.
2. The carbonation resistance test results showed that impregnant and epoxy had the greatest repair effect after one week, but epoxy/impregnant showed approximately 10% higher performance after four weeks. The performance of the impregnant repair decreased over time, and it is concluded that epoxy/impregnant repairs are most effective for concrete structures exposed to carbonation over a long period of time.
3. The chloride resistance test results confirmed that repair methods including impregnant had a penetration effect 2-3.5 times greater than the epoxy repair method. This is because epoxy repairs involve penetration at the concrete interface, whereas impregnant blocks chloride penetration from the outside due to its interface protection and waterproofing.
4. For freeze-thaw, both the relative dynamic elastic modulus and durability index were greater than 80% after 300 cycles when the exposure ended for all the specimens. For impregnant repairs, the relative dynamic elastic modulus exhibited a greater reduction rate as the number of freeze-thaw cycles increased. The reduction rate was low when the cracks were repaired using epoxy or epoxy/impregnant. As for the compressive strength after freeze-thaw, the reduction rate was less than 20% for all the repair methods. The methods that included epoxy were strongest.
5. As discussed, the crack size is an important factor when concrete structures are repaired. However, the strength and environmental factors also have a significant effect.  
The results confirm that epoxy is most effective for strength, epoxy/impregnant for carbonation, impregnant for chloride, and epoxy or epoxy/impregnant for freeze-thaw. To secure more accurate data, more repair materials, methods, and cracks will be examined in future research.  
Conceptualization, T.-K.K. and J.-S.P.; Formal analysis, T.-K.K. and J.-S.P.; Investigation, T.-K.K. and J.-S.P.; Methodology, T.-K.K. and J.-S.P.; Project administration, J.-S.P.; Resources, T.-K.K.; Software, T.-K.K.; Supervision, J.-S.P.; Validation, T.-K.K. and [PERSON]-S.P.; Visualization, T.-K.K. and [PERSON]-S.P.; Writing--original draft, T.-K.K.; Writing--review and editing, T.-K.K. and [PERSON]-S.P. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Smart Civil Infrastructure Research Program for the Ministry of Land, Infrastructure and Transport of the Korean Government, grant number 17 SCIP-B128496-01.  
Not applicable.  
The data presented in this study are available on request from the corresponding author.  
**Acknowledgments:** This research was supported by a grant (17 SCIP-B128496-01) from the Smart Civil Infrastructure Research Program funded by the Ministry of Land, Infrastructure and Transport of the Korean government.  
**Conflicts of Interest:** The author declares no conflict of interest.