WHAT IS GUNITE? 

There are a number of methods for swimming pool construction including:

 

Gunite/Shotcrete

Reinforced Concrete Block and Liner

Cast In-Situ

Stainless Steel Panel

Concrete Block Cavity/Reinforced Concrete

 

However, gunite is arguably one of the most popular and preferred methods of swimming pool construction.

So, what is gunite?

 

Gunite is a method of concrete application that utilises the high pressure spraying of concrete to achieve a monolithic reinforced concrete structure.  With a dry mix application, the concrete material is fed into a hopper, where it is pumped at pressure through a hose where it is initially mixed with water at the nozzle, and pneumatically applied at a high velocity directly to the swimming pool external formwork/reinforcement to achieve a monolithic concrete shell.  The ’nozzle’ man controls the quantity of water injected at the nozzle, and the placement of the material, therefore an experienced and competent nozzle man is essential. 

There are similar methods of application, often referred to as ‘shotcrete’, where the concrete material is fed into the hopper as a wet-mix, although the pressure required to pump the wet concrete mix is generally larger than that of the dry mix method but the rebound (waste material) is generally less than that of gunite. 

 

The terminology for swimming pools infers that gunite = dry mix and shotcrete = wet mix, however the term shotcrete actually encompasses both dry and wet mix techniques, with ‘gunite’ initially being a trade name.

 

Gunite/shotcrete is used in various other construction applications including:

  • Rock armament and protection

  • Tunnel linings

  • Artificial rock construction 

Advantages of a gunite/shotcrete pool:

 

  • A monolithic structure means the potential points of leakage (cold joints) are significantly reduced

  • The application process lends itself to layers of the concrete being applied, and thus the nozzle man can be confident that the application density of the concrete is sound, with no hollow areas or improper compaction to worry about.

  • The flexibility of gunite allows easier construction of curved walls and areas in swimming pools and water features.

  • As there is no requirement for formwork on the application side, the RC structure can be cured very quickly after installation, whereas with shutter and poured installations, the concrete has to set sufficiently for the formwork to be removed prior to any curing.

Things to consider:

 

  • The nozzle man has to stand at a distance away from the sprayed surface, therefore gunite may not be suitable for very narrow channels or other such limitations

  • Compared to in situ cast concrete, there is more wastage, often referred to as rebound.  Rebound is the constituent material that doesn’t adhere to the wall during the spraying process, however a good nozzle man and mix design will keep the amount of rebound to a minimum. 

 

If you have any questions about the gunite method, or indeed any other method for the construction of water bodies, then please do not hesitate to get in touch