Pouring slabs and columns in a single pour (not recommended) 1

[cliff234]

I am looking for the requirement in ACI 318 that prohibits the pouring of columns and slabs together in single pour. This practice is not recommended because it can lead to shrinkage cracks at the interface between the top of the column and underside of the floor slab.

I seem to remember a statement in ACI 318 (or perhaps another ACI document) discouraging (prohibiting?) this practice, but I can’t find it. Does anyone know where it is? Thank you!

 

[cliff234]

Never mind. I found it! ACI 318-08, Section 6.4.6.

"Beams, girders, or slabs supported by columns or walls shall not be cast or erected until concrete in the vertical support members is no longer plastic."

 

[bookowski]

I'm pretty sure that somewhere else, maybe in 301, it gives 1 hour (?) as a timeline for the "no longer plastic". In my area it is very common to pour slabs and columns in one day. They do all the walls and columns and then come back and start on the slab. I've never seen any indication of plastic shrinkage cracks at the interface.