[giansean]

Hi All,

I took advantage of the warm weekend weather (for Connecticut at least) to extend a 6" slab about 21". Total area was 21" x 47" x 6" so it's not very big.

I have read a lot about how to deal w/ concrete when it's cold (below 50). The work was finished by noon yesterday so it's already been setting for more than 24h. Even though it did not freeze last night (got to about 35F) I put about 20" of straw and tarps over it. I took the stuff off in the morning as it was sunny and warm thinking it would stay warmer. The surface was still moist when I took it off but drying out now. Seems to be setting up ok but not sure if I should mist/wet it at all before nighttime. It is supposed to freeze tonight however so if that is putting it at risk even when I put back the straw/tarps then I'll just leave well enough alone. It is not going to be holding anything too heavy (an AC condenser) so I'm ok with whatever works.

Any advice appreciated!

 

[gregzoll]

50 degrees is Spring weather. 30 is too cold. If you picked up a trailer of pre-mix, they would have told you what temp that the mix will cause problems. Concrete heats up by thermo reaction from the chemical compound. If you were to point a laser temp reader at it, you would see the temp rise as it cures.

That area is not much, and would be cured in a couple of hours. Put the tarps on and plenty of straw and it should be fine. If you want to double check, call a local mix yard.

 

[giansean]

Thanks.. so I guess more water is a no no at this point. I just used regular Quikrete from the big box. Tried to keep it as dry as possible just in case. It does seem to be doing fine though so far.

 

[SeniorSitizen]

I poured Quickcrete side walks 2.5" thick in the center in those temperatures, no reinforcement, didn't cover with anything and they've been there over 30 years and doing well. Idiot fork lift driver from Lows drove on them loaded with shingle bundles and they stood the test.

For yours, no water now. It'll be just fine.

 

[giansean]

Thanks everyone!

 

[gregzoll]

The additives can speed up the cure time and also make it last a little longer.

Keep in mind that Concrete is always curing. The older it is, the stronger it gets.

Worse case scenario if you had a bigger pour, would be placing heaters to blow under the covers.

Less water, dryer mix within Quikrete's spec's, you should be fine.

 

[MI-Roger]

Keep it tarped and insulated with straw. The chemical hydration reaction will keep the concrete warm enough. No additional water, the tarp will prevent water loss and keep the surface of the concrete damp enough to gain all the advantages of a "wet cure".

 

[jomama45]

I agree, leave the straw on for a few days at least. The general rule of thumb is that concrete shouldn't freeze until it reaches at least 1500 psi in strength, which could be 3-5 days, maybe longer, for Quikcrete in colder temps.

Just for future reference, concrete in cold regions that are prone to regular freeze-thaw conditions should contain air entrainment, which Quikcrete does not contain. It's not uncommon to see Quikcrete peel/delaminate after the first winter HERE in WI.

 

[ront02769]

Put your straw and blankets on it. Leave it, and stop worrying. As others have said, concrete generates heat while curing....plus if you take a 50 degree lump of whatever and leave it out at 30 degrees, it doesn't freeze instantly....ranger it takes a while....by which time it will be day and the sun will hit it. Ron

 

[Canarywood1]

Just FYI as jomama stated,it shouldn't freeze until it reaches 1500 psi, use a high early mix and you'll have 1500 psi in one day.

 

[jomama45]

Just FYI as jomama stated,it shouldn't freeze until it reaches 1500 psi, use a high early mix and you'll have 1500 psi in one day.

You can certainly do that with sight delivered ready mix, but "Quikcrete" is alot slower from my experiences, even their 5000psi high early. About the only thing we've found that sets fast is the fast-set red bags. We typically don't bother wasting the money on the 50# bags though, and just pour enough "Hydraset" into the regular bags to get good set.

Either way, I won't pour any of it outside w/o adding my own air entrainment.........

 

[giansean]

So far we've been pretty lucky with barely below freezing temps even at night. I didn't bother checking it today since it was raining most of the day so I'll just let it ride. It definitely would have been a job I'd have preferred to do in the spring but I need to move my AC condenser that my idiot HVAC contractor installed directly in front of the electric meter, which the town didn't seem to appreciate

Thank you all for the invaluable advice!

 

[stadry]

have been curious about that - adding air to bagg'd conc - how to ? dosage ? product ?

IF i'd thought about then, would've asked quikrete guys at woc in vegas,,, not that we get lots of extended freezes down here

thanks, guys !

 

[Aggie67]

FYI, for anyone that reads this in the future, Sakrete makes (and the big boxes carry) high early accelerants for cold weather pours.

 

[jomama45]

have been curious about that - adding air to bagg'd conc - how to ? dosage ? product ?

IF i'd thought about then, would've asked quikrete guys at woc in vegas,,, not that we get lots of extended freezes down here

thanks, guys !

My ready-mix suplier has "super totes" of all of the admixtures they use, including air entrainment. I usually stop there and get a quart when I need it. It goes a LONG way, something like 3-4 ounces per cubic yard, so I dilute it in the shop with water or water reducer to get a more accurate measurement for small batches in the field.

 

[Canarywood1]

You can certainly do that with sight delivered ready mix, but "Quikcrete" is alot slower from my experiences, even their 5000psi high early. About the only thing we've found that sets fast is the fast-set red bags. We typically don't bother wasting the money on the 50# bags though, and just pour enough "Hydraset" into the regular bags to get good set.

Either way, I won't pour any of it outside w/o adding my own air entrainment.........

I totally agree with the air, i understand that Quickcrete has a fast set that gets 7000psi in 28 days, and 3000 psi in 3 hours.

 

[giansean]

Here's the one-week later view for anyone interested. Still a little moist as I just took off the tarp/straw and it has been raining lately.

Not too shabby for my first concrete work ever

 

[Oso954]

Removing the forms and post a pic will draw more comments. The forms can hide a lot of signs, good or bad.

 

[stadry]

you're on your way - congrats !

 

[giansean]

Removing the forms and post a pic will draw more comments. The forms can hide a lot of signs, good or bad.

Great timing and indeed you're right. I had just popped off the forms and come back to post pics of what I found. At least it's not cracked

Welp looks like the dryer mix bit me in the butt a little. I should have realized when I was finding it so hard to float but since it wasn't really a showpiece and I was in a hurry I just let it go. Most of these edges will be buried so hopefully I can get away with filling in the sides with some quick dry cement patch and no harm done inside.

What could I have done differently besides adding more water? (again, I made it intentionally dry due to the freeze) Would temping or working it into the sides more have helped prevent this?