I used to b e a Civil engineer. Concrete is not going to gain much strength if poured in really cold weather. Do they have some super special secret additives up there?
An Alaska mix, first off we are using Type 3 cement with a 2% calcium chloride accelerator. Mixed with hot water this stuff licks off in only 30 minutes, or less If I agitate it too much. You do NOT dilly dally around with this stuff, it can flash over if you let it stay in the drum too long, its only 20F, they also cover the footers and heat them. We do this all the time up here.
Lol
No shock we both were on same page...