Curing time for concrete and multiple pours

[jbeall]

Hi All,

I remember being told by someone in the homebuilding industry that you could do multiple pours of concrete within a certain amount of time, and that they two pieces would actually cure together and become one, single piece of concrete.

But, I don't remember how long I had to do the second pour and have it all cure into one solid piece.

I'm working on a project that will use some concrete footers and then short concrete pillars on top of the footers. I'm not sure we'll be able to get it all done in one pass, so I'm thinking of pouring the footers one day, and then pouring the pillars (with sonotube-like forms) the next day, on top of the footers. So, I need to know how much time in between the two pours. 12 hours? 24 hours? Days?

Thanks for any feedback!

-Josh

[Studio43]

For some structural work it's imperative that concrete pours happen in a manner that will allow the concrete to cure as one. It may be that separate pours will bond together to some degree over time.

Your work sounds as if it not one of those cases. Since the loads are going to put a compression load on the concrete. It's common to pour the horizontal portion first(footing), let it cure for a few days then pour the vertical portion (pier). What you described sounds like a pier footing or spot footing for a deck.

It can't hurt to have some vertical rebar to tie the to separate pours together

[jbeall]

Ok, I think what I'll be doing is then is pouring the concrete footers, with several feet of rebar sticking up out of the footers (4 feet enough?).

I'll then come back after two weeks and pour the 6 foot concrete pillars.

[jbeall]

Does that sound reasonable?

[jbeall]

In particular, I'm wondering if two weeks is long enough to let the footers cure. Do we need to wait longer than that for them to be good and solid before we put the pillars on them? Those pillars are going to weigh around 1200 pounds, if my math is right (16" diameter, 6 feet tall).

[jbeall]

I'm also wondering if I need to keep coming back and wetting down the concrete each night--I've heard that's necessary to get it to cure properly.