I’d like to set my new mailbox tomorrow. I’ve got the hole dug, the post and unit all ready. The temps for the next several days will be highs in the upper fifties lower sixties, lows in the thirties, but above freezing. Plus this will be in a 20 inch hole so the ground temp is between that. When digging, I didn’t encounter any ice or frost so I believe the ground temp is above freezing and shouldn’t get below freezing.
I’d really like to get this chore taken care of, should I do it? Are there any concerns about ruining the pour at these temps. The concrete bags I have are nothing unusual with no additives to account for hot or cold temps, the recommendation on the bag is to do it between 50 and 75 degrees. I’ll start in that range but at night and in the ground, I think the temps are closer to 40.
Shouldn’t be a problem. You can place concrete down to about 25F without any additives. That said, wet concrete will freeze and you can have spalling when it thaws. But it’s a post hole, so no sweat.
I work with a lot of concrete, but for large stuff like footings and slabs and grade beams. There are ASTMs and codes in IBC and ACI that specify the temperature ranges for all types of concrete. Generally, temperatures below 50F are detrimental to early strength, below 40F and strength development is greatly retarded. At freezing, strength development is absent. But we are talking about a weight for your mailbox, not something that needs to develop any real strength. As long as it is above freezing and it isn’t disturbed nothing is going to happen.
if the ground isn’t frozen then it will be unlikely to freeze. keep it covered over night.
not the best temps but its a post hole and not likely to fall apart unless earthquake.
And if earthquake then !worry = mailbox.
For a mailbox post we always just place the post and dump the dry mix around it. Tamp it a little and pour on a bucket of water. Easy peasy!
I have half a mind to ask what a mind temp is, but I won’t.