The final stage of the pool shell construction is the all important placement of the concrete. A special concrete mix called Spraymix is used in pool building. Spraymix uses smaller aggregate, a higher cement ratio, lower water ratio and a range of concrete additives, all of which combine to create a very strong waterproof concrete.
The concrete is pneumatically placed, which means the concrete is sprayed at high pressure onto the walls and floor of the pool using a concrete pump and a compressor. The use of a concrete pump allows for pools to be constructed in areas where a concrete truck would never be able to gain access.
Once sprayed onto the pool walls the surface of the concrete is “cut” and shaped to the desired wall thickness which is usually a minimum of 150mm. Once the concrete spraying starts it must continue until the pool shell is completed. For the next two weeks the concrete is left to cure. The curing process is slowed by adding water to the concrete shell as often as possible. The slower the cure, the stronger the concrete.