Plaster pour 2 days after new concrete?

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R

RickAg

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Dec 1, 2021
13
Indio, CA
Close to finishing out an awful pool experience, and am a bit worried at the moment.

PB just poured a couple of additional pool steps today that were missed in the original shotcrete shoot.

They intend to do the plaster/stonescape install by Saturday.

Is it possible to plaster over concrete that has only cured for a couple of days? Ambient temps are between 45-70 right now.
 
2 days doesn’t sound like enough time for the concrete to fully cure but that depend on the mix they used.

Can you give us more details on exactly what they did and what concrete they used? Was it just mixed on site and poured? Was there a truck?

@AQUA~HOLICS might have an opinion on this issue …
 
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It's been a frustrating build process, the PB has disappeared multiple times. Here's the rough timeline so far:

Feb '22 - Dig & Rebar
Mar '22 - Plumbing, electrical conduit, etc
Apr '22 - Shotcrete
May '22 - Added additional steps & bench missed in plan (Quikrete used for these items)
May '22 - Decking (stamped concrete deck all the way to pool line for coping)
June '22 - Tile
Dec '22 - Equipment install
Jan '23 - Added final bump steps and shallow end step

So the shotcrete has been in place for a few months. They added a bench in the deep end and shallow end steps a couple of weeks after the initial shotcrete pour. I believe quikrete was used for these additions

For the steps that were added yesterday, it looks like a Dry Mortar was used: IMG_4908 Medium.jpeg


New steps added yesterday:
IMG_4900 Medium.jpegIMG_4902 Medium.jpeg

I see a bunch of cracks in the mortar steps that were poured yesterday. Is this problematic?

IMG_4906 Medium.jpeg



The bench along the deep end that was poured concrete after shotcrete:
IMG_4905 Medium.jpeg
 
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I’d put a stop on the plaster ASAP.

You cannot use mortar mix as a replacement for structural concrete. Mortar mix is for laying bricks, blocks, or stone. Also, those steps should have had a rebar cage in them that is epoxied into the main pool structure. You have a mess on your hands there and I suggest you put a hold on things until the PB can correct the deficiencies
 
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JoyfulNoise said:
I’d put a stop on the plaster ASAP.

You cannot use mortar mix as a replacement for structural concrete. Mortar mix is for laying bricks, blocks, or stone. Also, those steps should have had a rebar cage in them that is epoxied into the main pool structure. You have a mess on your hands there and I suggest you put a hold on things until the PB can correct the deficiencies
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@JoyfulNoise

Appreciate the info! Sounds like I get to have some more fun conversations.

Do you know of any documentation or building standards I could cite on the correct procedures here? I'm sure the answer I'm likely to get is "we know what we're doing, it's fine"
 
Just spoke with them and they are going to come back and re-do all the mortar steps with concrete. 🙌

Assuming the new concrete is completed today - is it safe for them to plaster tomorrow or Saturday? Or does the concrete need to be allowed to cure for a minimum period of time?

I'm not looking for them to rush the plaster, but they seem heck bent on sticking to the plaster schedule. They are ~8 months late on the project as it is. I certainly don't want to rush on the critical last step.
 
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RickAg said:
@JoyfulNoise

Appreciate the info! Sounds like I get to have some more fun conversations.

Do you know of any documentation or building standards I could cite on the correct procedures here? I'm sure the answer I'm likely to get is "we know what we're doing, it's fine"
Click to expand...

Perhaps send a question into the American Concrete Institute (ACI) and ask them to provide any information on the use of structural concrete in swimming pools and/or the differences between concrete and mortar mix.

The fact of the matter is, as @JamesW said, if this builder thinks that mortar mix is a one for one substitute for structural concrete, then their ignorance is outstanding. You should consider what options you have on cancelling the contract and trying to find someone else to finish the pool.
 

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RickAg said:
Just spoke with them and they are going to come back and re-do all the mortar steps with concrete. 🙌

Assuming the new concrete is completed today - is it safe for them to plaster tomorrow or Saturday? Or does the concrete need to be allowed to cure for a minimum period of time?

I'm not looking for them to rush the plaster, but they seem heck bent on sticking to the plaster schedule. They are ~8 months late on the project as it is. I certainly don't want to rush on the critical last step.
Click to expand...

The steps need to be formed with some rebar and that needs to be tied into the main pool structure or else you risk the steps moving relative to the pool during thermal cycling.

This is not an afternoon fixit process. It needs to be done correctly and the concrete needs time to cure. I would hazard a guess that the concrete itself needs a minimum of 7 days to even get close to its final compressive strength.

You really need to slow the roll on this contractor. They are in rush to get your job done, probably because they are losing money on it, and they are being sloppy.
 
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RickAg said:
Assuming the new concrete is completed today - is it safe for them to plaster tomorrow or Saturday? Or does the concrete need to be allowed to cure for a minimum period of time?
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Most references recommend allowing the concrete/gunite/shotcrete to substantially cure before plastering.

What plaster brand are you getting?

Maybe ask them what they recommend since they are warrantying the plaster.
 
What is the recommended cure time for shotcrete pools and spas so that shrinkage cracks in finished tile work can be avoided?

Concrete, when applied using the shotcrete process, or cast-in-place, needs to cure for 7 days.

Water is the best curing method (7 continuous days).

Curing compound can be applied, but the membrane film that is formed will have to be removed by sand or water blasting (5000 psi [34.5 MPa] is recommended) before the plaster or tile can be set (it will create a bond breaker if not removed).

There are curing compounds with a dissipating resin, which means after about 30 days in the sun, the material will break down.

In either case, it is a good practice to pressure wash the concrete surface to remove the grit and dust out of the pours so that the plaster and tile will have a good bond.

This is normal, everyday concrete curing practice that helps to prevent shrinkage cracks.

The concrete being applied should have a water-cement ratio (w/c) of 0.35 to 0.45.

Having the w/c at 0.40 at a 2 to 3 in. (50 to 75 mm) slump will keep the water demand low to help minimize the shrinkage.

Wet-fogging freshly placed concrete before the curing process begins will also help prevent shrinkage cracks.

shotcrete.org

What is the recommended cure time for shotcrete pools and spas so that shrinkage cracks in finished tile work can be avoided? - American Shotcrete Association

Concrete, when applied using the shotcrete process, or cast-in-place, needs […]
shotcrete.org shotcrete.org
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Some pool builders like to wait 28 days.

There are fast setting concrete mixes that set much faster and gain high early strength.

I would wait at least 7 days with regular concrete.

See what the plaster manufacturer says.
 
JoyfulNoise said:
Perhaps send a question into the American Concrete Institute (ACI) and ask them to provide any information on the use of structural concrete in swimming pools and/or the differences between concrete and mortar mix.

The fact of the matter is, as @JamesW said, if this builder thinks that mortar mix is a one for one substitute for structural concrete, then their ignorance is outstanding. You should consider what options you have on cancelling the contract and trying to find someone else to finish the pool.
Click to expand...
I think it's more incompetence on the builder's direction, guidance, training, and oversight to their employees or subs completing work.

I flagged the use of mortar rather than concrete, and there was no pushback or trying to convince me that it was the right product choice. I did see a used masonry drill bit and rebar scraps leftover form the work yesterday, so I'm fairly confident they at least did tie rebar into the new steps. When they come to chip out and re-work with concrete I'll be able to validate that assumption.

The pebble/plaster product is Stonescapes. I discussed concrete curing times with the local NPT Store, and the general sentiment was 7 days for curing would be a significantly safer timeframe.

They are 8-9 months late on finishing this pool, an extra week shouldn't hurt anyone too much at this point.
 
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I am going to jump in and share some links to help you get a good plaster job. Yeah the plaster job that needs to wait a bit.

Ten Guidelines for Quality Pool Plaster Best one of all
All Plaster Finishes Should Last 20 Years
Not All Color Pigments are Good for Pools How to pick a good color for plaster.
A Plastering 'Watch List' | Professional Watershaping | Watershapes
Trouble Free Pool
Trouble Free Pool

It is a lot of info but worth going through as I have a feeling your PB will not be so good at helping you start up the new plaster.
 
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