I'd like to pour a foundation as an addon to the house, about 100 sq ft. It would be done Monday midday, rain is expected thurs or friday. Should I wait or get some plastic and cover it or what?

I don't want to use any quick-cure stuff as I understand they can weaken the pour.
Thanks, KarlJay

Forgot to add, this is Sacramento and the outlook is upper 70's. The area to be poured is not in direct sunlight. 16~18" footer and 4" inner.

 

it will only need 24 hours to become weather tight.

unless you are talking about freezing cold, which i don't think you need to worry about.

 

Pour away brother. The rain on Thursday will only serve to wet the cured concrete which is actually beneficial.
Used to live in Sacto on Robertson, our biggest problem pouring there was trying to slow the cure in the dry summer heat.

 

The 2 biggest weather concerns with pouring concrete are freezing temps before it is cured, and hot dry weather that dries out the water before it has a chance to cure (concrete cures by hydration, not evaporation - the water becomes part of the concrete so if it dries out you get weak concrete). Rain during a pour is an issue if it is heavy, but not a day or more later. Heck, even rain a couple hours after finishing wouldn't be an issue if you cover it with plastic.

 

I'd go so far as to water the surface of the concrete on Tuesday and Wednesday and not wait until Thursday for it to get rained on. As was mentioned, concrete likes having the water present - it will cure harder than it would in dry conditions.I'd wet it down every day for a week.

 

Just don't water it too soon, or you'll wash the slip off.