free fall concrete
free fall concrete
(OP)
I am working on a job that is all concrete using a tunnal form the walls are 6" and has one row of rebar in the center
the concrete is falling about 8' is there a code that would keep me for pouring concrete or is this within code perameters
the concrete is falling about 8' is there a code that would keep me for pouring concrete or is this within code perameters






RE: free fall concrete
The question is really can you pour the wall without segregation (paste at bottom and rocks on top)?
RE: free fall concrete
I agree with jike that it should be noted in the provisions if it is a concern. Most state DOTs have a provision limiting to 5' freefall but that is not applicable here is my guess.
Regards,
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RE: free fall concrete
RE: free fall concrete
And another thought... buying the concrete in the fall when it's free is much better than paying for it in the summer.
Mike McCann
MMC Engineering
RE: free fall concrete
A greater concern is the length of time required for the placement, the upper part of the rebar cage will be well coated with concrete as it falls. You will want to complete the pour before this (thin) concrete coating on the upper rebar has time to set - degrading the final concrete/rebar bond.
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RE: free fall concrete
RE: free fall concrete
Segregation can be a problem with the aggregate bouncing off the rebar.
Dik
RE: free fall concrete
RE: free fall concrete
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RE: free fall concrete
RE: free fall concrete
You are correct if there is adequate space. For this case (6" wall with rebars in center) would be almost impossible. The concrete placement might have to accomplished by making several lifts using sliding form or other methods.
RE: free fall concrete
Watch out with cowboying the pour, Ive seen the aggregates seperate with a high pour, especially when it hits rebar on the way down, get a good vibrator and us it ALOT if you attempt this.
RE: free fall concrete
If you buy in on the FHWA drilled shaft concrete placement recommendations you can drop concrete 80' and not suffer ill effects.
One reason this is done is due to the amount of testing required for drilled shafts. Many state DOT require Crosshole Sonic Logging (CSL) and coring down into rock. Both the coring and CSL bear out that the concrete is placed as expected and consolidated fine.
So unless major testing is to be done for mid-height walls I don't recommend being so open as to allow extensive free fall especially with central reinforcing.
Regards,
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