Interesting thread. I've got a home builder pouring a slab in my neighborhood right now and temps are getting very low soon. It's dropping into the 30s and 40s in the next few days and the 20s on Monday. We'll see if they use blankets, but I doubt it. This builder is garbage. Thankfully it's not my house, but I feel bad for the homeowner if this would be an issue.
Do I pour my slab Friday or not? Help OB!
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Last: 1 day ago by Build It
Thunderstruck xx said:
Interesting thread. I've got a home builder pouring a slab in my neighborhood right now and temps are getting very low soon. It's dropping into the 30s and 40s in the next few days and the 20s on Monday. We'll see if they use blankets, but I doubt it. This builder is garbage. Thankfully it's not my house, but I feel bad for the homeowner if this would be an issue.
Most home slabs are garbage, its why foundation repair companies are so prevalent. Unfortunate, but true.
Just want to say thanks to all for sharing their knowledge on this. Very helpful for those planning to build. Great thread and the reason the OB is the best.
Sooooo... did we pour?
It ain't Friday yet. 
Gunny456 said:
It ain't Friday yet.
You definitely don't want them pouring on ***IT Friday.
Well that's what the OP has on his thread title. I didn't say do it on Friday.
I think we've scared him out of pouring
I had a project that was right across the street from a new neighborhood development (this was years ago now). Our specs on concrete were pretty tight, especially on time. No matter how much negotiating, whining, arguing, getting real world data, etc. I did the EOR wasn't budging on the batch time component of the specs. Which unfortunately for Cemex meant that more than one truck was rejected from our jobsite. Our spec was 45 mins, usually I could get it up to an hour but not this job.Thunderstruck xx said:
Interesting thread. I've got a home builder pouring a slab in my neighborhood right now and temps are getting very low soon. It's dropping into the 30s and 40s in the next few days and the 20s on Monday. We'll see if they use blankets, but I doubt it. This builder is garbage. Thankfully it's not my house, but I feel bad for the homeowner if this would be an issue.
Every single one drove across the street, found a crew and sold the concrete to them. I watched them dump stupid amounts of water into the truck to try to freshen up the mix (and because it makes it easier to place and work). Looked like soup coming down the chute. But that is typical for residential work, and it makes for slabs that crack pretty easy (the design of most home slabs doesn't help either, nor does the absolute lack of subgrade prep or proper concrete placement and cure). By this time that concrete was probably an hour and a half after batch, if not more.
While that concrete was easy to work and so soupy it was nearly self leveling, it was also maybe half the design strength it should have been after it cured. There is a reason that you have certain water:concrete ratios in designs, because it absolutely makes a difference in quality and strength of product.
This information is why I wanted you to find and comment on this thread.
Lmao... In my defense, I hadn't finished my coffee yet, and I'm off work tomorrow.Gunny456 said:
It ain't Friday yet.
I'm a structural engineer in the Amarillo area. If you still need help and want a more thorough conversation, feel free to give me a call.
https://www.fortestructural.com/
https://www.fortestructural.com/
We place concrete all the time in cold weather. Concrete needs to stay above 40 degrees to cure. We use heated water, and heated aggregate, if it's really cold we use additives that accelerate the curing.
I've placed concrete in -2 way up north. If you know what you're doing it's no big deal and happens everyday across America.
Your question is does your contractor know what's he's doing?
I've placed concrete in -2 way up north. If you know what you're doing it's no big deal and happens everyday across America.
Your question is does your contractor know what's he's doing?
Hardest place I ever placed concrete was Amarillo. That 40 mile an hour dry wind blowing over it makes finishing a giant pain in the ass.
I know that. I was having some fun. That's why the smiley face. Don't feel bad…, so I go to the neurosurgeon today and tell the nurses aren't they glad it's Friday.
See what you did to me!
And I can't give my self the excuse I had not had coffee yet.,,, I was just a pure Goober!
See what you did to me!
And I can't give my self the excuse I had not had coffee yet.,,, I was just a pure Goober!
Not to derail but neurosurgeon doesn't sound like a check up. Hope all is okay with you Gunny.
Build It said:
Hardest place I ever placed concrete was Amarillo. That 40 mile an hour dry wind blowing over it makes finishing a giant pain in the ass.
Dang right! Throw in the low humidity and scorching sun and you've got yourself a slab pour. A guy has to figure it out quickly up here.
I know this is diverging from the original thread, but - what is the process of doing a foundation the "right" way? I am assuming it is something like this. I would be interested in everyone's comments.
1.) Hire engineering company to pull core samples and provide a design. Is this always necessary? If you were on straight sand, would you really need to go this far for instance?
2.) Have the pad built with select fill. Pack with a bulldozer and let it get rained on for 6mo to pack it down.
3.) Have the concrete company come dig the beams, set the forms, and rebar. Verify measurements on everything to make sure it is following the design.
4.) After the pour, wait a couple of hours and then run a sprinkler 3-4 times a day for a week, assuming you don't have access to burlap.
The reason I am asking is that I had a 36x50 metal building done a few years ago. Looking back, I think the contractor did some things wrong. This was on sandy loam soil. He hauled in the select fill and compacted it with a skid steer. Poured concrete - 24"x24" beams around the perimeter, one through the center running the long direction (at my request) and 2 across the short direction aligned with the 2 center I beam supports. 1/2" rebar both directions. This used 3500# mix with 4" on the flats.
I parked a cattle trailer and tractor in it a month later and had cracks in both spots where there was load and in several other places. Some were so bad the crack was actually offset.
1.) Hire engineering company to pull core samples and provide a design. Is this always necessary? If you were on straight sand, would you really need to go this far for instance?
2.) Have the pad built with select fill. Pack with a bulldozer and let it get rained on for 6mo to pack it down.
3.) Have the concrete company come dig the beams, set the forms, and rebar. Verify measurements on everything to make sure it is following the design.
4.) After the pour, wait a couple of hours and then run a sprinkler 3-4 times a day for a week, assuming you don't have access to burlap.
The reason I am asking is that I had a 36x50 metal building done a few years ago. Looking back, I think the contractor did some things wrong. This was on sandy loam soil. He hauled in the select fill and compacted it with a skid steer. Poured concrete - 24"x24" beams around the perimeter, one through the center running the long direction (at my request) and 2 across the short direction aligned with the 2 center I beam supports. 1/2" rebar both directions. This used 3500# mix with 4" on the flats.
I parked a cattle trailer and tractor in it a month later and had cracks in both spots where there was load and in several other places. Some were so bad the crack was actually offset.
OP done peaced out on this thread
Or maybe standing at the concrete company checking the additive measurements? LOL
Yes sir. You are spot on. I'll know more next week. MRI and nerve conductivity test coming.
Much obliged for the caring. Much obliged.
Much obliged for the caring. Much obliged.
Bonfire97 said:
I know this is diverging from the original thread, but - what is the process of doing a foundation the "right" way? I am assuming it is something like this. I would be interested in everyone's comments.
1.) Hire engineering company to pull core samples and provide a design. Is this always necessary? If you were on straight sand, would you really need to go this far for instance?
2.) Have the pad built with select fill. Pack with a bulldozer and let it get rained on for 6mo to pack it down.
3.) Have the concrete company come dig the beams, set the forms, and rebar. Verify measurements on everything to make sure it is following the design.
4.) After the pour, wait a couple of hours and then run a sprinkler 3-4 times a day for a week, assuming you don't have access to burlap.
The reason I am asking is that I had a 36x50 metal building done a few years ago. Looking back, I think the contractor did some things wrong. This was on sandy loam soil. He hauled in the select fill and compacted it with a skid steer. Poured concrete - 24"x24" beams around the perimeter, one through the center running the long direction (at my request) and 2 across the short direction aligned with the 2 center I beam supports. 1/2" rebar both directions. This used 3500# mix with 4" on the flats.
I parked a cattle trailer and tractor in it a month later and had cracks in both spots where there was load and in several other places. Some were so bad the crack was actually offset.
There are so many things that need to go right to get a good slab. Decisions are often a balance between the best option, the owner's budget, site conditions and the contractor's ability. Keeping the slab wet for the first week is one of the best things you can do, but there's no single thing that will guarantee a successful outcome.
The foundation design is another thing. The foundation needs to be designed for the loads imposed by the building.
schmellba99 said:
Also, if it isnt cured right it will be crap as well. You dont just put it on the ground and walk away and magically it is good.
To add to that, 1 hour from batching is hitting the danger zone for time. We reject trucks after 45 mins. I have seen it start to flash at just over an hour before. Higher psi mix has more portland, more susceptible to flashing.
The standard is over two hours from batch time . Couldn't imagine kicking a 45 minute old tru.
So put sprinklers on sub freezing temperatures. So what should the air content be for cured concrete and not curing concrete.
Sorry for the late update, but as you can imagine, we had our hands full, plus some out-of-town travel added to the mix.
Thanks to everyone, including Gunny who went the extra mile to dig up some good intel from a friend of his in the concreate pouring business.
We were leaning towards delaying the pour but it came down to the final hour and we had to make a decision. We weighed the risk/odds and decided to proceed with the pour last Friday, around 2:30am because:
I'll report back in a few weeks as temps and weather changes. Thanks again!
Thanks to everyone, including Gunny who went the extra mile to dig up some good intel from a friend of his in the concreate pouring business.
We were leaning towards delaying the pour but it came down to the final hour and we had to make a decision. We weighed the risk/odds and decided to proceed with the pour last Friday, around 2:30am because:
- We have had the forms up now for over a month. The long-range forecast at the decision point, showed a low probability of being able to pour anytime in January with a very wet (and cold) outlook ahead. The thought of keeping the forms stable for 2+ months carried its own risks.
- We were coming into the pour with a warm ground (a high of 65 degrees later that day), unlike what we'd face in the coming weeks as cold spells become more frequent.
- Several "experts" (i.e. ACU certified, specialists, and engineers) recommended the pour given the variables and type of mix we'd be doing (along with a minor amount of additives, and higher than average psi).
- Last minute weather updates moved slightly favorable/warmer for the coming 3-day danger zone (from the low teens, to 20 degrees, though recently again that has changed).
- We implemented post-pour protection (36+hrs): one base layer of poly/plastic sheeting + a 20-inch layer of hay (13 round bales covering 9,000 sqft) + a top layer of poly/plastic sheeting to hold the hay down, with scattered bricks on top of it all for the wind. This will stay 1 week, until temps no longer drop below 40 degrees.
- A few samples were taken (we'll have the results later on). The breaking point is expected to range from 5,000 to 6,000psi. Much higher than spec'd.
- We placed multiple temperature monitors on the slab. While the current ambient/air temperature is 32 degrees this evening (will drop to 21 Tuesday), the slab top temperature is a toasty 64 to 70 degrees. I'm looking forward to checking the temps on Tuesday morning.
I'll report back in a few weeks as temps and weather changes. Thanks again!
Great job. I love it when a plan comes together.
And I especially like the plastic and hay blankets. Looks like they did everything you asked of them!
And I especially like the plastic and hay blankets. Looks like they did everything you asked of them!
Lonestar-aught-six said:schmellba99 said:
Also, if it isnt cured right it will be crap as well. You dont just put it on the ground and walk away and magically it is good.
To add to that, 1 hour from batching is hitting the danger zone for time. We reject trucks after 45 mins. I have seen it start to flash at just over an hour before. Higher psi mix has more portland, more susceptible to flashing.
The standard is over two hours from batch time . Couldn't imagine kicking a 45 minute old tru.
When you build large civil structures, 45 mins is almost always the spec time limit.
2 hour concrete woukd have to have to be about a 9+ slump.
Lonestar-aught-six said:
So put sprinklers on sub freezing temperatures. So what should the air content be for cured concrete and not curing concrete.
Air is 4-6%, measured at the same time slump on site is taken. Usually, some variations depending on the design and what the structure is. But usually in that range.
Lowest i have been able to go is 3%, highest was 9%.
So when's the break in dance? Every big slab deserves a street dance.
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Deerdude said:
So when's the break in dance? Every big slab deserves a street dance.
Hell yeah! A slab party!
Looks like you did everything right. Glad it worked out.
Great job! This is the way. Your guys knew what they were doing.
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