Most people are unaware of the difference between shotcrete and gunite. Some builders across the US prefer shotcrete, while others prefer gunite. There isn’t a big difference in quality when applied correctly. Our preference is shotcrete.
The products are very similar; they are both concrete products that are pumped through a hose under pressure and then sprayed over the steel structure until all steel is covered by around 3”. After the gunite or shotcrete is sprayed, covering the steel sufficiently, the applicators use trowels and other concrete tools to shape and fine-tune the walls, steps, floors, and other pool features before it dries.
The primary difference between shotcrete and gunite lies in the application of water to the concrete mixture. Shotcrete is a concrete product that is mixed with water before it is pushed through a pressurized hose. Gunite is a dry concrete product pushed through a pressurized hose, with water spraying the dry mixture as it exits the nozzle.
People wonder whether gunite would be weaker than shotcrete, since some of the concrete powder may not fully hydrate after leaving the nozzle. Gunite is actually quite strong, but a byproduct called rebound can occur when the mixture is not properly hydrated, causing it to fall to the ground rather than sticking to the wall. Shotcrete can also produce rebound, but it is a fraction of the amount produced by gunite. Good pool builders remove rebound, but some attempt to use it on the floor of the pool or to fill steps because they don’t want to waste the product. Doing so is a short-sighted mistake because the rebound can settle and cause cracking.
We prefer shotcrete because it is wet when pumped through the nozzle, allowing virtually all of the concrete to be used without concern for diminished quality. We also prefer shotcrete because it generates less waste, helping us keep a cleaner jobsite. When builders have to throw rebound out of the pool, large amounts of concrete rebound end up around the structure. Using shotcrete keeps the site much cleaner.
Both shotcrete and gunite are good products for a pool, but we prefer shotcrete. And, in the Treasure Valley, shotcrete is the standard for concrete pools.