Curing Concrete Question - Cold Weather

[Tidybuoy]

I just poured a new driveway. Weather has been in the 60's daytime and mid-40's at night. Until the day of the pour. We had a sudden cold snap and the night time temp dipped to 28 degrees (the day of the pour). The temp was under 32 degrees for about 6-8 hours and then back in the 50's. The second day (which also was the 2nd half pour) dipped to 32 degrees for 5 hours and then back to 50's.

It's been 2 days and weather is now high of 66, low of 38.

I asked the concrete guy if I should hose down the driveway and he asked me if I have hard water. We do have hard water but not so bad that it spots windows dramatically. The concrete guy told me to wait a day and then I could hose off.

Just curious - why would he question the hard water? I will ask him when he stops by tomorrow but thought I would ask here.

[masraum]

Sorry, I can't answer your question, but that's a nice looking driveway.

[id10t]

If you have really hard water and it is caused by lime in the water (and not some other mineral) then I guess it could be possible to throw off the chemistry of the reaction that allows the concrete to cure, esp. if the minimal temperature is already affecting it.

[cabmandone]

Hard water could leave calcium deposits on the crete and discolor it. Also if you have Iron it could iron stain. He's probably just giving the sealer time to cure would be my guess. The sealers are all water based at this point.

[Evans, Marv]

^^^^^ This. I don't remember it getting that cold very often in Fresberg. I did snow there once back in the early '60s though.

[wdfifteen]

Originally Posted by cabmando

Hard water could leave calcium deposits on the crete and discolor it. Also if you have Iron it could iron stain. He's probably just giving the sealer time to cure would be my guess. The sealers are all water based at this point.

They put sealers on soft concrete now? I just had a pour done and the contractor said he would be back in a month to seal it.
It got into the 20s the night of the pour and he was concerned. Curing concrete is an exothermic process, and we put straw over it to help keep the heat in. I used an infrared thermometer which read surface temps in the 30s when it was 24 degrees out.

[cabmandone]

Originally Posted by wdfifteen

They put sealers on soft concrete now? I just had a pour done and the contractor said he would be back in a month to seal it.
It got into the 20s the night of the pour and he was concerned. Curing concrete is an exothermic process, and we put straw over it to help keep the heat in. I used an infrared thermometer which read surface temps in the 30s when it was 24 degrees out.

A lot of contractors have gone to a sealer/curing agent that they spray on once the concrete is set. I haven't been involved with much cold weather (our cold that is) concrete jobs so each guy could do things a bit different.

[rusnak]

Calcium will speed up the curing. They actually use calcium to help it cure if rain is expected. Pretty much all of Fresno well water is hard btw. City water less so, but still

[DanielDudley]

Tarp it or plastic.

[Zeke]

Originally Posted by wdfifteen

They put sealers on soft concrete now? I just had a pour done and the contractor said he would be back in a month to seal it.
It got into the 20s the night of the pour and he was concerned. Curing concrete is an exothermic process, and we put straw over it to help keep the heat in. I used an infrared thermometer which read surface temps in the 30s when it was 24 degrees out.

2 different things, curing sealer and post cure sealer. The first one washes off.

AFA the temps go, as long as the new pour doesn't freeze while it still has a high water content, it will be OK. The exothermic reaction should protect it for the first day unless it gets just way to cold for an extended amount of time. Any real danger and the contractor would have covered it to keep the heat in.