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[486]---Please Come Back---We Love You!

[486] said:
it's in a basement that ain't heated and ambients are down touching freezing overnight
should be like 50f surface temp on the ground in there yet

but the mix is going to be coming in at about 40-50f which is below where it'll be making any heat of its own since it isn't curing at all yet, right?
Normally you'd have hot water to warm up the cold aggregate and sand and shit, but their boiler's broken.
Dunno, guess I'm going to find out, then feed it as much heat as a 40 gallon water heater can put out. Could probably stack foamboard on top of it too, but it might get too hot if I do that
iirc it gets real weak if it is cured over 90f, but it doesn't cure at all below like 64f?

just a bundle of "dunno man"
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The low end for "normal" placement in most states (speaking from a highway/DOT perspective) is 50 degrees. Curing doesn't create the heat but the heat is what helps to cure. The heat is caused by the chemical reaction from the hydration of Portland cement. It'll still kick off fine in the 40's, it just may take a bit longer. Might lose a tiny of of strength too. If this is something overly structural, might see if they can bump the portland up a 1/2 sack or something if you're worried about it.

But if it's going to get that cold at night, that's probably a bigger concern, at least for the first few days. We'd used insulated curing blankets, but they're $$. If you have any insulating material laying around, you can make it work. Even rolls or chunks of fiberglass batt, foam board or whatever. Just throw some plastic down so you don't fuck that stuff up.

Or, it doesn't take much to heat a small area if you can tent it off. Even an electric space heater would probably be enough to keep the frost off.
 
What about piping a kerosene heater into the basement? Wouldn't that help make the top coat cure more better?

I'm not a concrete guy.
 
bgaidan said:
The low end for "normal" placement in most states (speaking from a highway/DOT perspective) is 50 degrees. Curing doesn't create the heat but the heat is what helps to cure. The heat is caused by the chemical reaction from the hydration of Portland cement. It'll still kick off fine in the 40's, it just may take a bit longer. Might lose a tiny of of strength too. If this is something overly structural, might see if they can bump the portland up a 1/2 sack or something if you're worried about it.

But if it's going to get that cold at night, that's probably a bigger concern, at least for the first few days. We'd used insulated curing blankets, but they're $$. If you have any insulating material laying around, you can make it work. Even rolls or chunks of fiberglass batt, foam board or whatever. Just throw some plastic down so you don't fuck that stuff up.

Or, it doesn't take much to heat a small area if you can tent it off. Even an electric space heater would probably be enough to keep the frost off.
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yeah it'll probably be totally fine and I'm just mother henning it

so the heat's from the hydration of the cement but that is separate from the concrete curing?
I thought they were one in the same, since once it starts heating up it makes a lot more heat, one of them exothermic reactions that feeds into itself. If it ain't got enough heat at the beginning (cold water and cold dry shit) then it wouldn't begin to harden properly, just sit there and have the water evaporate out until what's left freezes and busts up what little bond strength it had

Guess I had the tubing under pressure for a few days and it hasn't leaked, but putting water in it will reduce my ability to tell if I puncture it during the pour...
Maybe I oughta set up all the shit so I can dump the air and put the water in the tubing/heater right after floating it.
 
We use LA40 to repair concrete buildings (much more change in thermal mass temps being exposed) down to 20 degrees with blankets and no issues. Can't speak to a new pour but ground temps can't be below freezing already I'd think. I think a slower curing process would be the only downfall. People pour garage slabs here touching 30 with blankets and no issues

Glad your back!
 
[486] said:
so the heat's from the hydration of the cement but that is separate from the concrete curing?
I thought they were one in the same, since once it starts heating up it makes a lot more heat, one of them exothermic reactions that feeds into itself. If it ain't got enough heat at the beginning (cold water and cold dry shit) then it wouldn't begin to harden properly, just sit there and have the water evaporate out until what's left freezes and busts up what little bond strength it had
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At the temps you're talking about, the difference in strength or any physical properties will be next to undetectable. I don't know what happens if you try to cure in extremely cold temps without insulation or supplemental heat - I guess if you started near or below freezing with the mix and everything stayed there or got colder, you could halt hydration and just be left with a pile of rubble. Dunno...never tried it. :laughing:
Higher temps are much more risky than lower. Especially with really thick shit (like 5' or more). Too much heat generated while curing can lead to severe cracking and in the worst cases cause it to just crumble. In this part of the world, I've had to deal with that far more than a little cold weather. Water chillers are more common than heaters in the work I've done.
 
Another thread totally derailed to concrete tech!!!!
:shakes head:


I thought the slower the cure the better????

I like your idea (486), on keeping the air in the line, then switching to some Luke warm water after your done finish work!!!!
:smokin::smokin::smokin:


Get the 3D GoPro’s setup and git to slingin!!!
:flipoff2::flipoff2::flipoff2:
 
bgaidan said:
Too much heat generated while curing can lead to severe cracking
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Bet that's related to how everything expands and contracts as it heats and cools, concrete is expanded when it cures then when it cools it pulls apart from itself. So pouring it cold might be a big advantage there, have it in there tight to put some outward tension on the walls that have been backfilled for a couple winters now and might be bowing in a little bit (or I just didn't pour the walls straight to begin with)

Seen pictures of where stuff got too hot during curing and got crumbly like you describe too, can just chip away big chunks with a claw hammer.

Think I'm gonna get 1.5% of NCA (they recommended at least 2%, but my last two pours were at 1 and 0.5% with hot water)
then extend the floor heat lines so I can put the water heater on it if it doesn't start firming up after a few hours.

Got two guys saying "maybe" and the nuclear option if neither of them can show up is to borrow one of the guys from where I work/usedtowork/dunno but during business hours with real short notice that's kinda a big ask so I'm really trying to avoid that.
Gregj50!!!!! said:
Get the 3D GoPro’s setup and git to slingin!!!
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sorry but I'm already scared of posting pictures any more with how the surveillance state has gotten
too easy to miss something in the censoring step after deleting the exif data and resizing to reduce the readability of packaging labels carelessly left in frame
fuckin ugh
Anyways video where I can be seen or heard ain't happening.
 
bgaidan said:
But if it's going to get that cold at night, that's probably a bigger concern, at least for the first few days...
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When the local Wally World was being built, they hired Chinese nationals to do the concrete slab in the wintertime 🥶. The workers had built bonfires 🔥 everywhere & slaved during the day/overnight to treat/cure the foundation-
 
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