What could cause this calcium buildup on the exterior of my pool?

[willerd]

Hi all. New homeowner with a pool that was built in 2019.

Could anyone provide some insight into what may be causing this calcium deposit? This can’t just be from overspill, right? I understand that ASR might be an issue (built in 2019, gunnite, Central Texas), but there is zero cracking inside the pool interior, and there have been no new cracks since we purchased the house one year ago. So I am unsure.

https://imgur.com/a/TOLzM2K

Any insight that y’all may have will be greatly appreciated. Any ideas?

Thanks!

 

[ajw22]

It is Efflorescence - Further Reading

 

[JamesW]

That is likely a skimcoat on the gunite and water is bleeding through the pool wall and then through the skim coat causing efflorescence.

Tap on it to see if it sounds hollow.

 

[willerd]

That is likely a skimcoat on the gunite and water is bleeding through the pool wall and then through the skim coat causing efflorescence.

Tap on it to see if it sounds hollow.

Thank you both for your replies. Very interesting! It does not sound hollow - there is a single spot with a crack that does, but there’s no efflorescence in that area.

 

[JamesW]

You will probably need to remove some of the top layer to see what is happening below the skim coat.

What does the builder say?

 

[ajw22]

Show us wider pictures of where that area is in the pool and what is on the other side of it?

 

[willerd]

You will probably need to remove some of the top layer to see what is happening below the skim coat.

What does the builder say?

The builder is appears MIA at this time. Is replacing the removed skim coat a job I can do myself, or will I need a pool builder to do it?

Show us wider pictures of where that area is in the pool and what is on the other side of it?

I'll do my best to get better pictures once the sun is directly overhead, but here is what I have now of both the exterior, and interior side of where the split is:

https://imgur.com/a/2llj59N

 

[JamesW]

Is replacing the removed skim coat a job I can do myself, or will I need a pool builder to do it?

I have no idea what you can or cannot do.

Only you can decide if you have the ability to do a specific job.

I do not know exactly what the finish is.

Maybe it is part of the gunite and maybe it is a separate applied finish.

Was the finish applied after the gunite?

 

[JamesW]

Most likely, you will need to start by removing the top layer to determine if the layer is flaking off or if it is part of the original gunite.

Once the top layer is off, you can look at the gunite to see if the cracks are only in the top layer or if the cracks go through the gunite.

ASR - Concrete Cancer - Austin, TX

Has anyone had experience with this issue? Alkali–silica reaction - Wikipedia. 3yr old - fresh water pool with cracks all over the walls Apparently the Shot Crete company (among others here) had not mixed right and messed up a number of pools. Edit by Jim R. thansk

www.troublefreepool.com

What to do with ASR?!

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Preventing ASR

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Note: I am not recommending that you begin to start digging into your wall.

Only you can decide what you feel comfortable with.

Do your Due Diligence and Research before deciding what to do.

I am only providing general opinions and observations and not specific advice.

Contact some local professionals to see what they think.

 

[ajw22]

Please post pictures to the forum...

Picture Posting and Resizing - Further Reading

www.troublefreepool.com

 

[willerd]

Great, thank you JamesW. I've definitely read through those threads. Without providing a diagnosis, and only in your opinion, do you think what I have resembles ASR? I saw that you had a great deal of skepticism for the number of cases we were seeing in Central Texas, and I still have my hopes up.

And sure, thanks ajw22, my apologies, I posted to Imgur since the photos were too large but I will ensure all photos in the future are posted here.

 

[JamesW]

Without providing a diagnosis, and only in your opinion, do you think what I have resembles ASR?

Insufficient information to provide a preliminary diagnosis.

I would strip off the top layer so that I could see the actual gunite.

The top layer might be simply delaminating and cracking or the gunite might be cracking.

 

[ajw22]

Do you want to discuss efflorescence or ASR?

Water is wicking into the gunite shell, probably external to the pool water, and finding places to come out creating efflorescence. I doubt you will be able to seal up your pool structure now to prevent that. Most gunite pools are buried in the ground and you never see what may be leaching on the exterior walls.

I would not dig into your pool walls yet looking for ASR. Wait and see if extensive cracking develops. You say your builder is already MIA. Is there any benefit to you to find out you have ASR now versus later?

 

[willerd]

Ah, no benefit if the end is the same, my thought process was that if it is not ASR/terminal failure of the concrete that there may be a way to repair existing cracks and to prevent further cracking in the future. It sounds to me like a crack in the gunnite is irreparable and will result in extensive cracking anyways?

I'm bringing in a structural engineer to look at the foundation since there is some separation and empty space underneath the pool (visible in pictures) so I was thinking that this may be a cause for cracking also, and that treating the foundation may help prevent them in the future as well.

We unfortunately do not have the funds to rebuild, so we're trying to elongate the lifespan of our pool as much as possible.

 

[JamesW]

Did you have an engineer for the initial build?

Did you have a retaining wall or other support to stabilize the ground and prevent sinking?

Is the pool still level or is it going off level?

 

[ajw22]

Gunite shell cracks that are not caused by ASR can be repaired by concrete staples or epoxy injection.

There are a bunch of Youtube videos showing concrete staples being used to repair gunite cracks.

If the staple repairs are done properly with quality materials and an experienced crew it should hold stronger then the surrounding gunite.

There are a few different crack repair techniques and concrete staples will be stronger then just an epoxy injection crack repair.

If the pool is on unstable soil then it may need stabilization with piers to prevent cracking.

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www.troublefreepool.com

 

[willerd]

I was not the original homeowner who built the pool, so I am unsure about the presence of an engineer or if there are any stabilizing elements. I received the original building permit from the city but there are very few details other than the original company who built the pool. They are fortunately still in business, but I have not been able to contact them yet. Hopefully they are just on an extended vacation...

I am hoping that a structural engineer that I bring in will be able to determine whether it is unstable ground - I am still in the process of determining who to bring in, since I want to find someone with water shaping/pool experience.

Sounds to me like my best action plan is to
1. Hire a structural engineer to see if the soil is stable and if the pool requires stabilizers if they do not already exist
2. Hire/consult with a pool builder to discuss the process of stripping off a panel of skim coat to check to see if the gunnite is cracked
3. If the gunnite is cracked, determine whether it can be patched with concrete staples or if it shows further signs of ASR.

 

[JamesW]

Geotechnical engineers study the soil and have knowledge of the geology under the ground.

Structural engineers design structures above ground.

What Is The Role Of The Structural Engineer Versus The Geotechnical Engineer? By Neil Opfer

Structural Engineers need quality Geotechnical Information to develop the best design possible given the soil conditions present at the site.

smartsensesystems.com

 

[ajw22]

Are there any signs of cracking in the interior of the pool?

Concrete staples are only needed when cracks go fully through the gunite. Gunite is typically 6 to 10 inches thick.

There are often exterior shrinkage cracks that do not go fully through the shell and voids the gunite missed that are not structural issues.

Gunite/shotcrete and all concrete is not waterproof. The plaster and tile waterproofs the pool interior.

The exterior wall cracks and efflorescence are not indications of structural issues although I understand everyone in your area is concerned about ASR.

So far you have not shown any signs of serious issues in what you posted.

 

[JamesW]

Both structural and geotechnical engineers are involved in pool design, but they have different areas of expertise:

Geotechnical engineers Study the conditions of the ground and soil, and provide recommendations for the structural design of the pool's foundation.

Geotechnical engineers analyze soil samples taken from borings drilled into the ground.

They identify any unusual or unsuitable soil conditions, and recommend mitigating measures.

Structural engineers design the foundations and structures above or within the ground.

They create drawings and specifications, and perform calculations.

A standard pool plan is a structural engineering plan that includes designs for common site conditions.

Geotechnical and structural engineers are both civil engineers, and their work often overlaps.

The practice of geostructural engineering combines the knowledge of both types of engineers to design site retaining walls, micropiles, slope reinforcement, and more.