Gunite vs. Shotcrete: What's the Difference?

What's the difference between gunite and shotcrete for a concrete pool?
Concrete pools can be made of either shotcrete or gunite. The difference is when the concrete mixes with the water. Shotcrete refers to wet concrete that's already fully mixed before it's shot out of a hose. Gunite is dry concrete mix that only mixes with water at the nozzle when it's sprayed.

This video also answers common questions like...

What's the difference between gunite and shotcrete?
What's the difference between concrete and gunite pools?
What's shotcrete?
What's gunite?
What is wet mix?
What is dry mix?
What is the construction process like for gunite and shotcrete pools?
What are the pros of gunite?
What are the cons of gunite?
What are the pros of shotcrete?
What are the cons of shotcrete?
Which should I use, gunite or shotcrete?
What is more expensive, gunite or shotcrete?

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[clintwalker]

I don't feel you done a fair job of explaining any differences to potential customers. First off shotcrete is the method of which the concrete is being pneumatically applied. Gunite is actually a trade name coined by Carl Akeleyhe as he is the man that originally came up with the process of pneumatically placing cementious materials This is to say whether it is a dry mix (gunite) forced through the hose by air pressure and water added to the mix by a nozzle at the end of the hose or it is premixed concrete pumped through the hose and air pressure is used at the nozzle to spray the material, both are still really shotcreted in place.
As you stated though "gunite" is the term used in the pool industry to indicate that the material being used is a dry mix of sand and cement pneumatically forced through the hose with water being added at the nozzle immediately before exiting the tip. Likewise "shotcrete" is the term used to indicate the concrete was premixed, generally at a batch plant where precise control over the mix formula can be obtained, delivered by truck, and placed in a high pressure pump capable of forcing this mixture through the hose and air is used at the nozzle to assist in the placement of the material.
As someone that has been in the pool industry for over twenty years and personally operated a shotcrete business for most of those years, I can give my honest opinions of what I think of both processes or material types or methods, whichever you chose to call the difference of the two.


Advantages for wet mix "shotcrete"
1) prebatched at a plant with tight control over mix formula and amount of water in the concrete
this helps assure strength of the finished product. The amount of water added to dry mix "gunite" is solely the discretion of the nozzleman.
2) different additives can help with placement and cure times needed for various weather conditions
one can add calcium to speed set times and help prevent freezing in cold climate or add retarder to increase set times in hot climate
3) Rock or gravel "crushed stone" is almost always added to shotcrete for additional strength
other materials such as fiber can also be added for additional strength, on the other hand dry mix "gunite" is strictly sand and cement
4) Since the concrete is mixed with the water already added there is a lot less rebound with shotcrete.
rebound is the amount of cement material that falls out of the air stream during placement or either just doesn't stick when it hits the surface it is being applied to. Since sand is heavier and less absorbent than the cement most of the rebound from dry mix "gunite" is mostly sand which needs to be removed from the floor before any new material is applied over it.


Advantages for dry mix "gunite"
1) since the mixture is dry right up until it leaves the nozzle the job can be delayed without major concerns of concrete setting up in the hoses, delivery truck or the equipment.
2) with the nozzle operator in control of the amount of water added to the mix he can adjust the consistency immediately to aid in applications that need to be tight enough to stand up on it's own such as when he is beaming the pool out or shooting in steps and benches.
** this advantage can immediately turn into a disadvantage as cement must have enough water to start hydration or it will never reach the cured strength the mix is designed for. This is solely left to the nozzlemans expertise and experience and cant possibly be tightly monitored or controlled.
3) Delivery time of the mix is not as critical as with wet mix "shotcrete". A load of wet concrete stuck in traffic for an hour or so can become useless or a job with no ready mix batch plant within reasonable driving time can cause a lot of grief to a shotcrete crew. Dry mix "gunite" doesn't suffer from this setback as the dry mix can remain in the truck indefinitely without consequence.


There are pros and cons to both processes and both have worked amazingly well for many many years. This is just to inform people of the difference and maybe help someone decide which better suits them and their needs.


With the owners permission I would like to include a link with more information on the process should anyone care to further their inquiry about the matter.

[mwoods]

1.5 minutes in on every video until you get to the actual content you came for is annoying.

[alpineflier]

Thank you for that tidbit of info. I had been wondering about the difference.

[davidrico]

Was a nozzleman for many years. One advantage of dry mix is it's reach. I have used over 600' of hose, up a very steep grade to apply it. Also dry mix can even be applied overhead. Wet mix is much faster. Still have not seen the use of the correct technique to minimize rebound and maintain thickness with a dry mix.

[tillmansr]

So one version is readymix (on site mixing of materials - gunite), whereas the other version is batched off site 'mixed ahead of time' (shotcrete), basically a 'zero' slump mix. Is this about right?

[markharder]

So the difference is entirely a matter of how it's applied? There's no difference in the composition of the cement itself?

[cinthiasmith]

Still unsure if there are any differences, that I would need to know as an owner? I am buying a home and it has a gunite pool. Is there any care issues that we will need to know that are different from the others. We've never owned a pool, so this is all new to us and we don't want to screw up the pool..lol I am a germaphobe, so would it be possible to drain all the water that's in the pool now, so I can clean the inside and then put clean, fresh water in it and if so will it cost me an arm and a leg? Lol

[KelsieP]

I just love these videos. You'e really helped us understand!

[joeyskyles]

Gunite is a sand base mix and shotcrete is a sand and stone mix

[dmaninthewall]

So I do this for a living at a steel mill but I want to hire a company that does shotcreat work with shotcreat equipment to build my house and pool with it
How do I approach companies

[Hugh_Jaynus_]

Well…some up the info he provided…in under 2 seconds. It depends on where it is mixed. Done. Did I beat the timer?

[wjf]

I'm enjoying your videos, and learning a lot from them. I do have a question....

I build Monolithic domes, and we spray foam against an airform, hang rebar and shoot shotcrete to create the dome, and it's all done on the inside. We inflate with 2 inches of water column and that keeps one inch of shotcrete sticking to the foam and rebar over head, and if we lose that pressure inside the dome before the shotcrete starts to cure, the shotcrete will fall to the floor.

Now my question is this, why don't pool builders ever spray foam on the ground to help insulate the concrete pool shell, like we do when building a concrete dome home?

I mean a dome is an upside down pool basically. I spray foam on the ground before pouring a concrete slab, so why not do the same with a pool, especially in colder climates so the pool retains its heat for longer use. Thanks and keep up the great work.

[pharpester]

Can you do a video on concrete cancer?

[davidbrokamp]

Not premixed in the hopper like he said
There are two hoppers the materials are mixed and shot dry down the hose

[Cristoesrey]

Had rain a couple of days before shotcrete.. about 2 inches of rain. Is it ok to shotcrete on wet soil? HELP . Don’t want to move forward if it is something I’ll regret

[irenepadre]

Hello thanks for info, machine used same for spraying of shotcrete and gunite right? i work in a subcon company here in uae, we do spraying of gunite/shotcrete works in swimming pool and piling

[austinphillips]

Gunite FTW and ALWAYS FTW. My family has been in this business for 50 + years and Gunite is the only way to go unless you want a vinyl liner. Now, there is nothing wrong with vinyl liner pools but the cost point comes down to what you are paying for. Gunite pools are far more expensive because they are not prefabricated molds stuck into the ground. If you want something unique and/ or something beautifully done to your exact specs, gunite is the only way to go.

[Rezorcful]

I'd rather you spent all 4 minutes talking about the difference instead of a rushed 2 minute one. After listening to you talk about nothing for 2 minutes..

[andyh]

If you are making a shallow in ground concrete pool from cinderblocks, rebar, sand and portland cement in a northern climate -- would it be more resiliant to cracks and leaks if you build it on top of a membrane / pond liner? (or is that not a good idea?)

[craigmonteforte]

thanks good video i grew up in South Florida i’m now 56 years old and i thought it was 2 different brands all these years i always knew that the Nozzleman was the key to getting a good pour the one thing i used to like watching was the Marsite guys troweling on that material in South Florida it was always a team of older African Americans that were super fast in my early 20s i worked installing ceramic tile on over the Marsite in i ground pools many commercial pools were doing that to lower maintenance costs and upkeep apparently the pool uses way less ch;orine as well ?