## 5 Conclusions  
This study applied a polymer coating known as SSS coating to concrete surfaces in order to improve their impermeability in high-pressure water environments. A series of impermeability tests were conducted to analyze the seepage regulation of the coated concrete and the failure mechanism of the coating after concrete cracking. The following conclusions can be drawn from the experimental results:  
1. The EMS coating promoted the permeation of the SSS coating and reacted with the uncured coating to form a composite protective layer. This process increased the adhesion of the SSS coating to the concrete. Moreover, the SSS coating did not separate from the concrete surface without cracks under a water pressure of 3 MPa. 2. As the water pressure increased, the average seepage height of the concrete also increased. High pressure also increased concrete compactness, resulting in a decrease in the concrete's relative permeability coefficient. Organic sodium silicate could improve the pore structure of the concrete, reducing the average seepage height and relative permeability coefficient of concrete by 35.5% and 58.3%, respectively, under the same water pressure. The SSS coating effectively improved the impermeability of concrete. The SSS-coated concrete was not penetrated, indicating that 3 MPa pressurized water cannot penetrate the SSS coating with a thickness of 0.5 mm within 24 h.
3. As the water pressure time increased, the average seepage height of the SSS-coated concrete increased, indicating that the SSS coating was ultimately penetrated by water. The impermeability of the SSS coating varies in different directions in contact with water. The SSS coating located on the top surface of the specimen indirectly enhanced the impermeability of the concrete. The SSS coating located on the bottom surface of the specimen directly prevented permeation. Compared with the former, the average seepage height and relative permeability coefficient of the latter decreased by 49.6% and 71.2%, respectively. 4. The impermeability of the SSS coating after concrete cracking is related to crack width and water pressure. When the crack width was less than 1 mm, the SSS coating could maintain impermeability under a water pressure of 3 MPa. When the crack width was greater than 2 mm and the water pressure was 1 MPa, the SSS coating deformed. As the water pressure increased, the SSS coating was punctured or torn due to stress concentration. Figure 10: The process of tear damage. **(a)** The crack width is less than 1 mm, and the coating has not been punctured; **(b)** When the crack width exceeds 1 mm, the coating extends; **(c)** The coating falls off due to concrete displacement; **(d)** The coating is punctured by the primer. This study focused on the effects of high-pressure water and crack width on the impermeability of the coating, and changes in coating thickness and crack number are also potential future directions. The research results can be applied to global hydraulic engineering and ocean engineering, which is beneficial for improving the service life of concrete in high-pressure water environments and is significant for engineering economics and safety. Conceptualization, B.T. and L.Q. ; methodology, L.Q. and M.X. ; validation, B.T., L.Q. and Y.X. ; formal analysis, B.T. and L.Q. ; investigation, Y.X. and X.Y. ; data curation, B.S. ; writing--original draft preparation, L.Q. ; writing--review and editing, B.T. ; visualization, J.W. ; supervision, X.Y. ; funding acquisition, M.X. All authors have read and agreed to the published version of the manuscript. This study was financially supported by the Natural Science Foundation of Sichuan Province, China (No. 2024 NSFSC0836) and the National Natural Science Foundation of China (No. 52109135). Not applicable. The original contributions presented in the study are included in the article. Further inquiries can be directed to the corresponding authors. We would like to thank [PERSON] for providing technical support.