Waterproofing Concrete 101 – Why It’s Important for Swimming Pools

For decades, swimming pool contractors such as Pleasure Pools have used concrete as a way to build swimming pools, to hold in the water to be enjoyed by family and friends. The process is a simple one, where the concrete (shotcrete/gunite) is blown over a substrate structure to hold the concrete firmly in place. A decorative finish is added to the pool shell, which will accept the water in hold it within itself.

To be effective, the swimming pool needs to be 100% waterproof and to prevent any leaking of H2O through any cracks, gaps or pores. However, exactly how should a contractor waterproof the swimming pool made out of concrete and what needs to be done if it still leaks water?

Permeable Concrete

Even though concrete can withstand pressure of up to 4,000 psi, its density and strength do not add to its waterproofing capacity. While concrete formulated in higher densities also have a greater resistance to water penetration, it still has significant molecular gaps and pores that allow water to permeate.

Concrete in colder areas seem to be more subjected to the negative effects of waterproofing. The water that can permeate into the concrete can easily become frozen which makes it expand. This can cause significant damage to the interior structure of the concrete along with any component that it is attached to.

Acids and Carbon Dioxide

To make matters even worse, water that is absorbed into concrete contains a mixture of acidic compounds and carbon dioxide. This can over time reduce the pH levels of any steel reinforcement (rebar) which could begin the corrosive process as the metal starts to rust. Within virtually no time at all, the iron content inside the rebar will begin to oxidize in areas where the steel is located near the concrete’s surface. This natural chemical reaction usually happens just below the finished surface and will cause significant corrosion over time.

Using a Crystalline Admixture

There are ways to avoid this problem. One includes an option where crystalline admixture can be added to the concrete before being poured. Sometimes, even with the extra cost it is the only option, especially when using concrete underground where it might be exposed constantly to water, in areas that suffer from higher water tables.

Because the process of mixing and pouring concrete along with waterproofing it, involves human effort, there is always the possibility that it will not be fully protected. Mixing a high moisture resistant shotcrete/gunite on the interior of the swimming pool might not be as waterproof as believed.

Getting to 100% Waterproof

Studies indicate that many of the failed swimming pools that tend to leak are usually a result of improper installation. Forensic tests indicate that waterproof products for swimming pools are rarely actually 100% waterproof. It is only when there is some catastrophic failure that the contractor or pool owner understands just how bad the waterproofing of that specific pool was performed during the installation process.

The only way to be assured that it is waterproofed, beyond its materials, is to add a layer of waterproof material over the concrete. In fact, chemistry alone indicates that there is actually no way to waterproof the concrete, without actually applying another layer of waterproofing to the pool shell.

If you would like to learn more about waterproofing for a potential pool project or for your existing pool, please contact one of our contractors today to have your specific questions answered.