concrete placement tolerances at column to slab interface
concrete placement tolerances at column to slab interface
(OP)
ACI-117 doesn't appear to give a straight answer on this. What is the reference for the concrete placement tolerance for top of column to bottom of elevated slab/beam. In other words how far into the bottom of the slab can the column below be over-poured or protrude into the slab above when the slab above is formed up and rebar is being placed.
The EOR says zero.
I understand that this is a function of how thick the suspended slab/beam is: the thinner the slab the more important this is. The engineer wants the full thickness of the slab/beam where the most shear is - the face of the support.






RE: concrete placement tolerances at column to slab interface
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: concrete placement tolerances at column to slab interface
RE: concrete placement tolerances at column to slab interface
RE: concrete placement tolerances at column to slab interface
RE: concrete placement tolerances at column to slab interface
In my personal view, slightly high will result in a socket which is unlikely to materially reduce strength or durability. If I had to put a value on it, I would require that the lower pour stop the greater of one bar diameter or the nominal large aggregate size below horizontal reinforcement to assist in consolidation around those bars. A smaller gap may result in partially embedded and improperly bonded reinforcement.
Slightly low should not cause problems in a properly detailed column (bars developed above the joint.) These joints should be rough.
I will bring up this issue as new business in the next 301. (We are wrapping up 301-15 now so I can't get changes started for that edition.)
Generally speaking, we should not expect unreasonable accuracy in construction. Enforcing limits where they do not matter will increase cost (and reduce the respect contractors have for us) without improving he safety and serviceability of structures.
RE: concrete placement tolerances at column to slab interface