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SHOTCRETE/GUNITE

SHOTCRETE VERSUS GUNITE. They all look the same to me, concrete spraying out of a hose, sticking to the rebar frame, and eventually hardening into a swimming pool. What’s the difference? To the uninitiated, shotcrete and gunite might appear to be identical processes, but there are subtle differences with each method, and pros and cons of each. Let’s start by mentioning that both are excellent methods for building a swimming pool, and both have been used extensively for years, with thousands of pools built using each method. Lots of the popularity of shotcrete or gunite comes down to the individual contractor and what he’s most comfortable using. Many contractors have simply been setup with one method and its associated equipment for years, and just never tried the other.


Gunite: First, the reigning champ. Gunite has been patented since at least 1911, so your grandpa’s dad was probably using it back in the day. It’s called ‘gunite’ because the dry concrete mix is shot out of a ‘gun’ at high speed using compressed air. The exact method of how it functions is fairly simple. Gunite itself is simply cement mixed with small aggregate and sand (making it by definition, concrete), that is pumped through a high pressure hose, dry. At the end of the nozzle for the gunite gun is another hose that feeds water, so that when the dry gunite is shot out, it mixes with water, allowing it to stick and ultimately cure and bond with whatever it comes in contact with. We all know that concrete is simply cement mixed with aggregate, and then mixed with water in a form, then cured – this is the way concrete has been made since the days of the Romans. Well gunite is almost exactly the same process except the mixture happens at the nozzle of the hose. Gunite has several things going for it, namely it’s shot out at high pressure, meaning that it becomes densely packed and very strong. It also cures fast and is very workable.


Shotcrete: Shotcrete looks on the surface to be applied in the same manner as gunite – concrete coming out of a hose at high pressure – yet there’s one important difference. Shotcrete is premixed at the concrete plant and can be engineered, which means that it can be designed to withstand certain high strength loads because the consistency of the concrete is established in a controlled environment – the concrete plant – rather than at the nozzle of the gun on site by a potentially unskilled worker. Shotcrete proponents really hang their hat on the engineered side of the equation, and it is definitely something to bear in mind when making a pool selection. Shotcrete detractors, however, claim that since the mixture comes out wet that it can’t be packed as hard as gunite can – therefore isn’t as strong, and this is potentially true in some cases. Shotcrete has all the advantages of gunite in that it can be formed into complex shapes as desired.


Both gunite and shotcrete pools have been in service for decades, and there are thousands upon thousands of pools in service today that are made of both materials. Either material is appropriate for concrete pool construction, and both materials need an interior finish such as plaster to remain watertight. You really can’t go wrong with either kind of pool construction method, and keep in mind that your pool contractor will usually be set up for one or the other methods, but not both, and will have the skill necessary to ensure your shotcrete or gunite pool comes out being the pool of your dreams.







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