If you’re considering building a new concrete swimming pool, then chances are you’ve heard the terms “gunite” and “shotcrete.” But do you know the difference?
Basically, gunite and shotcrete are different ways to apply the concrete. The determining factor of whether your pool is gunite or shotcrete has to do with when the water is added to the concrete. We use the term gunite to mean a dry concrete mix, and we call it shotcrete when dealing with wet concrete. The term “shotcrete” was approved by the American Concrete Institute in the 1950’s to essentially just refer to pneumatically placed mortar (read: using compressed air to apply concrete).
With shotcrete, the concrete is already mixed in a cement truck before you shoot it out of a hose, while gunite is a dry mix that combines with water at the nozzle when you spray it.
These types of mixtures are also used in other construction projects like retaining walls and parking structures, but we’ll stick to pools for today.
Concrete Pool Construction Process
Whether you decide to go with gunite or shotcrete, the construction process is essentially the same.
The process begins with measuring and excavating the ground where you want your pool. The plumbing gets installed next. From there, you install the tied steel rebar to reinforce the cage. Then it’s time to spray the concrete to encase the rebar. This is the point that you will either use gunite or shotcrete.
The next step in the construction process is to finish the pool’s shell and let the concrete cure. Once the concrete is set, you can install the tile. If you are building a patio, you will do that next. After that, all that’s left to do is apply the finish and enjoy your new pool.
With a gunite application, you would load the equipment with premixed dry material. Pool builders use compressed air to shoot the dry concrete through a hose to a nozzle, which is where you add the water. The wet-mix then sprays out onto the surface of your pool at a high velocity. The nozzleman controls the application, adjusting water levels as needed to get the right mix consistency. The process makes the concrete compress as you apply it.
Remember that shotcrete means that you’re working with a wet concrete mix. For this wet mix process, you begin with thoroughly mixed concrete. The wet concrete is delivered by a cement truck. Just like the gunite dry-mix process, shotcrete uses compressed air to shoot the concrete through a hose. The concrete sprays out at such a high speed that it bonds to itself where it is applied.
- Gunite is cheaper than shotcrete
- With gunite, you can stop and start the application without creating any weak points
- Super high strength with low shrinkage
- You can walk on the wet concrete without disturbing it
- Gunite is easier to clean up than shotcrete
- The hose is lighter and easier to use
- Because you add water at the nozzle, the concrete is very fresh when you spray it
- Gunite requires a much more experienced crew
- The hose can get clogged by the dry concrete
- Gunite can be very messy, it produces a lot of over-spray or rebound which can be tough to clean up
- The equipment requires a lot of maintenance
- Lower production rates than shotcrete
- The crew doesn’t have to be as skilled because the concrete comes already mixed
- The shotcrete process is faster than gunite
- Higher production rates
- You don’t need to add water
- Requires less equipment
- In most places, it’s easy to get the materials
- It’s easier to add specialized admixtures to the concrete
- If the hose gets clogged, it can be tough to clear which could be dangerous for the crew and property
- You may have to add water to help with the pumping
- The hoses are very heavy and are more challenging to use for the crew
- You can’t start and stop the application otherwise you will create weak points in the concrete
The Bottom Line
Ultimately both gunite and shotcrete work by spraying a wet cement onto the walls and floor of your pool. The difference is gunite adds the water to dry concrete as you spray it. Shotcrete begins with wet concrete, so you don’t need to add any extra water.
The bottom line is that both gunite and shotcrete have their advantages and disadvantages. The truth is both will produce a high-quality, watertight, durable swimming pool if you do the processes correctly. It really all comes down to what your builder prefers.
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It’s important that whether you go with gunite or shotcrete that you use qualified, trained contractors.
Hopefully, we’ve helped you better understand the difference between gunite and shotcrete today. Best of luck building your new pool!