Experimental Study on Improving the Impermeability of Concrete under High-Pressure Water Environments Using a Polymer Coating

The concrete lining of high-pressure water conveyance tunnels permeates under high-pressure water. Dense and hydrophobic coating can effectively improve the impermeability of concrete. However, the coating exhibits varying impermeability in different high-pressure environments, which can even lead to coating detachment or damage. The objectives of this study are to improve the high-pressure impermeability of concrete by using a polymer coating, and to study the varying impermeability through experiments. This study applied a polymer coating called SCU-SD-SP-II (SSS) to concrete surfaces, and it formed a composite protective layer with an epoxy-modified silicone (EMS) coating. A series of high-pressure impermeability tests were conducted to study the seepage regulation of the coated concrete and the failure mechanism of the SSS coating under cracks in the concrete. The results indicate that the SSS coating has excellent impermeability. Pressurized water of 3 MPa could not permeate the SSS coating with a thickness of 0.5 mm within 24 h. Under both external and internal water pressure conditions, the SSS coatings improved concrete impermeability. Additionally, the average seepage height and relative permeability coefficient of the latter decreased by 49.6% and 71.2%, respectively, compared with the former. After concrete cracking, the SSS coating could withstand 3 MPa pressure on crack surfaces smaller than 1 mm. When the crack width was greater than 2 mm, the SSS coating deformed under 1 MPa pressure. As the pressure increased to 2 MPa or even 3 MPa, the SSS coating was punctured or torn due to stress concentration. This study provides new insights into the impermeability of concrete under high water pressure.