Sequential Concrete Pour
Sequential Concrete Pour
(OP)
Hi All,
I'm working on a project where we are casting a reinforced concrete frame against an existing building to reinforce it. The contractor is behind schedule and has proposed a somewhat odd methodology to speed up the programme. Currently all the reinforcement is hung on the building and they are proposing to cast two floors, beams and columns in one day. They plan to allow the columns/beams on the lower floor to set partially and continue pouring the second level columns and beams. The formwork for the beams are propped and supported by the existing structure so we will not be loading the beams. The columns on the lower level will have to take the weight of the plastic concrete of the upper floor. I have initially objected to the idea suggesting that loading the column that has only achieved a partial set will impact the long term strength of the column. Is there anything wrong with my objection?
How are very large/tall pours undertaken to prevent lower pours from setting before the pour is complete.
Thanks
I'm working on a project where we are casting a reinforced concrete frame against an existing building to reinforce it. The contractor is behind schedule and has proposed a somewhat odd methodology to speed up the programme. Currently all the reinforcement is hung on the building and they are proposing to cast two floors, beams and columns in one day. They plan to allow the columns/beams on the lower floor to set partially and continue pouring the second level columns and beams. The formwork for the beams are propped and supported by the existing structure so we will not be loading the beams. The columns on the lower level will have to take the weight of the plastic concrete of the upper floor. I have initially objected to the idea suggesting that loading the column that has only achieved a partial set will impact the long term strength of the column. Is there anything wrong with my objection?
How are very large/tall pours undertaken to prevent lower pours from setting before the pour is complete.
Thanks






RE: Sequential Concrete Pour
I agree with your objections.
The tallest (fast) pours that I have been associated with were 3 ft. diameter columns for the piers of highway overpasses. The concrete quantity is very small, so it could be placed rapidly. The limiting factor is the fresh concrete's hydrostatic pressure that the forms can withstand. We limited height to 20 feet (3000 PSF). Manufactured steel forms were needed to withstand that pressure... and they were the ideal shape to do so - circular.
Even though the Contractor plans to let the lower level partially set, things do not always go as expected. Suggest you get the Contractor to address form design / construction - he may change his mind about very tall pours.
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RE: Sequential Concrete Pour
RE: Sequential Concrete Pour
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Sequential Concrete Pour
RE: Sequential Concrete Pour
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Sequential Concrete Pour
RE: Sequential Concrete Pour
dcarr....I agree with the two options but option 1 is too risky in my opinion. Prefer the two pours.
RE: Sequential Concrete Pour
I know. I contend that once you've achieved 2500 psi etc, it's a non-issue. Beams and slabs are poured on top of columns and walls at 2-3 day strengths that will be much less than this all the time. Heck, I spec most of my vertical concrete strengths at 56 day precisely because this is a non-issue.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Sequential Concrete Pour
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Sequential Concrete Pour
Thanks
RE: Sequential Concrete Pour
I don't think that it is much different tclat. If I understand your situation correctly, you will have the wet weight of only the upper columns loading your lower columns as the beam forms will remain in place longer. And that load will be pure compression. That's what, maybe 15 psi compression?
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.