Gunite

Also Known As: Shotcrete, Pool Shell

Gunite or shotcrete is the process of applying concrete to form or repair a structure, like an inground pool. It comes in two basic forms: dry gun (dry mix) and wet gun (wet mix).

The dry-gun method depends on a gunite rig that mixes and compresses aggregate and cement. This mixture is blown through a hose. At the tip of the hose, water is introduced, and the wet mixture is then blown onto the walls and floor of the pool to create the shape. In this method, it is easier to avoid excess water in the mixture, as only the amount of water necessary to hydrate the aggregate and cement is added. It is also easier to apply as the weight of the water is not being pushed through the entire length of the hose.

On the other hand, the wet-gun method uses pre-mix concrete, pumped onto the walls via a hose and nozzle. The makeup of the concrete mixture is controlled by a computer program, which can be adjusted on site. The ratio of concrete to water is higher in the wet-gun method of gunite than in cast-in-place concrete. This makes it dry enough to be applied to vertical surfaces, like the sides of a pool wall. The proper materials slump must be maintained throughout the process.

Because of the way gunite is applied, its very useful in atypical designs with walls of varying slopes. In addition, fewer joints are required, allowing for easier maintenance and sturdier construction.