Too cold for shotcrete?

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Titan7

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May 9, 2015
846
Peoria, AZ
So we are looking to have the pool shell shot on Thursday. I noticed that we will be getting down to 32 a few days later. I read that may be too cold for Shotcrete or watercuring if it gets under 40 degree. Do we need to get a large blue tarp and cover the pool and put a small space heater under it when it drops that low? Of course we missed our window last week when the lows were 40s & 50s.

Wanted to get unbiased opinions as I am sure the PB is gonna say no issue.

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Here is a thread that covers this questions and some other things to watch out for when the shell is being done:

Is it ok to shoot gunnite pool in the middle of winter?

HI I am researching potential probs for a gunnite pool shoot scheduled for this weekend (Dec 17) from a reputable pool contractor. That said, the contractor subs out this part of the pool build project. I am a landscape designer and in this case acting as GC for the project as well. My instincts...
www.troublefreepool.com www.troublefreepool.com
 
Any chance they can just delay it for a week or two to get past the cold snap?

Technically those lows are overnight temps and they usually only get that low for a few hours in the early morning. If the PB is willing to tent the pool, then a space heater could help.

I’d see if the PB is willing to wait … the shotcrete crew may be on a tight schedule so not taking slot on Thursday could cause lengthy delays.
 
I will discuss it tomorrow but I’m inclined to wait. Also, with temps that low I can’t water cure it so I don’t know how I water cure during the day and then not do it at night when the temps drop. I can pick up a blue tarp that will cover the pool and just weight it down on the top edges and place a space heater in the middle of the pool.

Waiting will allow me to just have a sprinkler on a timer and run it 24hrs per day.
not sure what to do but I’m sure I will get the “ we do this all the time without problems” line from them. You can drive drunk many times and not kill some body or get arrested but that does not mean it’s risk free or recommen.
 
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I think the watering concern is overblown. Concrete needs to be watered, yes, but it doesn’t need to be flooded. The surface simply needs to be wetted down with minimal accumulation in the deep end. People spend far too much time worrying about constantly watering a shotcrete structure and setting up sprinklers. It’s takes all of 30mins with a garden hose sprayer to completely wet down most pool designs. After around 7 days the shotcrete has reached 80% of its targeted compressive strength. Watering beyond that point doesn’t do a whole lot except to create a frog sanctuary in the deep end bowl. Simply wetting it down during the day and letting it ride overnight will be fine.

When my pool was built (hot summer months in Tucson), my PB told me to wet the pool surfaces down 3 times per day for the first 7 days and then once a day after that until the final 28 days was complete. My pool is fine.

The critical issue isn’t water, it’s temperature. Tenting the surfaces to retain warmth is more important. If the PB gives you the “it’ll be fine, trust me” line, then ask him if there will be any tenting setup after the shell is formed to retain heat. If not, does the shotcrete sub guarantee that the shell will cure properly? Ideally you’d like to have the shotcrete sub in the conversation.
 
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Well I spoke with the PB and they are giving me the “ we do this all the time”. We weather forecast has the low tomorrow Thursday at 41, then Friday-Tues 38, 37, 41, 35,33, 35. These are the lows.

they want to do shotcrete tomorrow.
should I ask for a core sample be taken at 28 days? Not sure where they do that or if a bucket of shotcrete can be set aside. Do I even want a hole taken out of the shell?

I asked about watering, tenting, heaters, etc, but have not gotten anything back.

Am I over thinking this and should just let them move ahead? I suggested waiting but they are well it could rain and cause dirt to fall into the pool🙄

thanks for suggestions
 

I have a question on cold weather shotcreting.​

I have heard that for shotcrete operations, the ambient temperature has to be 40°F (4.4°C) and rising.​

I am on a job, and the inspector said it only needs to be 35°F (1.67°C) and rising.​

The high for the day is expected to be around 45°F (7.2°C), then fall back into the high 20s F (–4 to –1.67°C).​

What would be your advice?​

Shotcrete is concrete and the same rules apply with respect to cold weather applications.

Cold weather is defined in ACI 306R, “Cold Weather Concreting” as “a period when, for more than 3 consecutive days, the following conditions exist:

1) the average daily air temperature is less than 40°F (4.4°C) and

2) the air temperature is not greater than 50°F (10°C) for more than one-half of any 24-hour period.”

ACI 306R is an excellent reference that provides recommendations for cold weather concrete placement and protection. A copy of ACI 306R can be purchased online at ACI’s Web site, www.concrete.org, from the Bookstore and Publications tab.

You can also download articles regarding cold weather placement from ASA’s Web site, www.shotcrete.org—click on “Shotcrete magazine,” go to the article search page, and type in “cold weather.”

I have a question on cold weather shotcreting. I have heard that for shotcrete operations, the ambient temperature has to be 40°F (4.4°C) and rising. I am on a job, and the inspector said it only needs to be 35°F (1.67°C) and rising. The high for the

Shotcrete is concrete and the same rules apply with respect to cold weather applications. Cold weather is defined in ACI 306R, “Cold Weather Concreting” as “a period when, for more than 3 consecutive days, the following conditions exist: 1) the average daily air temperature is
shotcrete.org shotcrete.org
 
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All surfaces receiving shotcrete should be above freezing. The mandatory requirements of ACI 506.2-13, “Specification for Shotcrete,” specifies:

“3.4.5 Cold weather shotcreting—Unless otherwise specified, shooting may proceed when ambient temperature is 40°F and rising. Stop shooting when ambient temperature is 40°F and falling, unless measures are taken to protect the shotcrete. Shotcrete material temperature, when shot, shall not be less than 50ºF. Do not place shotcrete against frozen surfaces.”

shotcrete.org

ACI 506R-16 discusses surface preparation requirements for various substrate surfaces and notes that for earth surfaces shotcrete shall not be placed on frozen ground. There does not appear to be any specific temperature requirement for other substra

All surfaces receiving shotcrete should be above freezing. The mandatory […]
shotcrete.org shotcrete.org
 

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You can purchase the ACI PRC-306-16 Guide to Cold Weather Concreting for $75.00 if you want.

I suspect that it will be fine as long as it stays above freezing the entire time.

Maybe put out a bucket of water somewhere and if the water never freezes over, you are probably going to be fine.

Maybe put one in the sun and one in the shade somewhere.
 
Looks like the weather says it will not get down any colder than 36 on next Monday. The avg temp will be 46-48, and they don’t care what I provide them, they said it will be fine. Would you suggest I get a core sample? They said $250 to do it. I guess this is done at 28 days? Would certainly prove they were correct or I was, lol.

getting a bit of light rain now, love pool building

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Titan7 said:
Looks like the weather says it will not get down any colder than 36 on next Monday. The avg temp will be 46-55, either way they don’t care what I provide them, they said it will be fine. Would you suggest I get a core sample? They said $250 to do it. I guess this is done at 28 days? Would certainly prove they were correct or I was, lol.
Click to expand...

A core sample is a good way to confirm compressive strength. It’s a small hole and it’s best to take a few samples. It doesn’t affect the structural integrity at all and the holes are filled with hydraulic cement after the sample is pulled. The plaster is what provides the waterproofing layer so the hydraulic cement is fine. Holes are punched into pool shells when they are drained and there is no hydrostatic relief so that they don’t float if the water table is high.

$250 is a rounding error for a pool build, heck … that’s a week’s worth of Starbucks runs for some people. I say its worth the confirmation in my opinion.
 
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I think I may go that route, with the core, I do need to find out what psi the shotcrete will be.

I also looked at the weather, we will not meet the criteria for cold weather based on the example above I looked at the avg temp is above 40 and there is at leas 12 hours at 50 and above for the 3 days following placement of the shotcrete.

Thank you for all the assistance, now I just need to have a chat with them tomorrow about PSI, curing, and NO Rebound. Love paying people to do this and making sure they do it correctly 🙄
 
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Looks good.

Keep it watered as-instructed but don’t go crazy. You should be making the surfaces wet but not turning the pool into a swamp. If water is accumulating in the deep end, then you’re overwatering it. I used my garden hose with a long spray wand attachment that had a “misting” option. That allowed for good control over wetting the surface.
 
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Thanks for the tips, it was a long day. I was up at 5:30 laying the Ram board in the street and sidewalk and plywood on the pavers, of course they didn’t do that🙄. They thought I was crazy, but I don’t want the street in front of my house covered with oil stains from commercial vehicles. I am already gonna need to reseal the asphalt in front due to the bobcats during excavation, nothing I could do as the plywood would just spin but at least I am keeping damage to a minimum.

Oh, and any thoughts on how to remove the scaling from the leak on the filter. Vinegar just laughs at it. I know it effects nothing but it just looks terrible and was caused from a factory mis alignment of the O rings🙄
 

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Are you in an HOA? Were you told that the asphalt needed resealing in the street? I would leave it unless specifically requested to address it. Most HOA’s need to reseal every 18-24 months anyway. So it will eventually get fixed.
 
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