Gunite Pool Construction

Whats the difference between Gunite and Shotcrete?

Generically speaking, Gunite is a term that is loosely used to describe material that is pneumatically applied.

Specifically speaking, Gunite and Shotcrete are similar in the sense that they are both a pneumatic or force applied material application. However, the difference between Gunite and Shotcrete is this:

The Dry process (Gunite) is a mixture of mainly sand and cement. The dry process is shot though the hoses like a sand blast operation with the water being applied at the very end of the hose. When applied to a pool, the crews mainly do the floors first due to the large amount of rebound produced. When the walls, benches and spas are shot, the crews must throw out the rebound. If any rebound is incorporated into the floor, a weak sand-like pocket will form. If it doesnt stick, it must be removed.

The Wet process (Shot Crete) is a mixture of sand, cement, small pea gravel and water. The wet process is brought out by a ready-mix concrete truck and pumped via concrete pump with the air applied through a nozzle at the very end, to spray the material in place. This method produces little or no rebound so the walls are applied first, then the floor shot last. All excess material pulled from walls can be incorporated into the floor area and then shot over. This can't be done with the dry process.

Pros verses Cons

With the wet process, the mixing of batches is done in a plant and is supervised by a qualified technician, utilizing sophisticated computerized technology in the batching process. The results are a truly monolithic pour and a more consistent product, as it is not mixed on site. This method can be more demanding on the applicators as the wet process has a limited time to place and finish from the time of being batched at the concrete plant. The dry process has an advantage for the applicator during periods of extreme heat as the dry process is mixed on the job site allowing more time to work. However, material consistency is relying solely on the one or two job site men that are put in charge of mixing for that day. Any anomalies in mixing will undoubtedly result in a weak spot within the shell.

While the wet process or Shotcrete includes stone and gravel in the cement mix, Gunite does not. The strongest mixes are generally regarded to have stone as the aggregate as the more varied the aggregate sizes are, the greater both the compressive and tensile strengths. Gunite uses less water to hydrate but the surface can be more porous. Proponents from either side will claim their method to be of the greater tensile strength and thus implying a stronger shell.

The Lido Difference

While every company will proudly defend their preference of process, we at Lido believe that the pros of the wet Shotcrete process outweigh the pros of the dry process. Certainly tensile strength is important but so is a monolithic pour. Lidos combination of the monolithic pour together with a substantial structural steel design, which incorporates a superstructure of 10mm reinforcement bars unified in a grid like network centered at 8 intervals and combined with a superior double ring bond beam. Material thickness at the top of the wall or bond beam is 8". The floor is poured at 12" thick with the higher stress areas along the cove are increased to 14". Indeed a foundation that ensures unprecedented shell strength and longevity.