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Re: Pouring Concrete Beam Monolithic with Concrete Column

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Michael,
 
I think the problem with placing the concrete in the supported structure before the concrete in the column has completed its plastic shrinkage that voids may develop in the junction; voids that may not be apparent. 
 
In a foundation with relatively light horizontal reinforcing in a horizontal grade beam crossing a deeper pile, I've seen a depression form in the top of the grade beam that has been screeded level.  As the column concrete undergoes shrinkage, I would expect the same effect.  However, heavy reinforcing in the slab or beam over the column may prevent the concrete in the slab or beam from following the column shrinkage downward, potentially producing voids at that critical location.
 
Nels Roselund
Structural Engineer
South San Gabriel, CA
njineer(--nospam--at)att.net