construction joint in concrete beam
construction joint in concrete beam
(OP)
Attached is a sketch of a portion of a foundation for a chemical storage shed. The Contractor wants to pour to the underside of the slab, remove the inside forms, and then pour the slab. Would that be acceptable?






RE: construction joint in concrete beam
Here's a couple of thoughts on it:
1. Yes you can place the horizontal construction joint at the level aligned with the bottom of the slab. Specify a 1/4" roughened surface throughout.
2. If the beam is spanning and takes significant shear, the two legs of the stirrups must now serve a shear friction function across your new joint in addition to the shear in the beam. This will require additional stirrups most likely.
3. Since the stirrups are now working in shear friction, they must meet standard hook requirements vs. stirrup hook sizes. This means that you must develop the stirrup hook past your joint by the hook development length, ldh.
4. The void you have below the beam - if it is a product that deteriorates over time, then you will need some kind of fill retainer on either side of the beam to keep the soil on the sides of the beam from sluffing into the void space over time.
RE: construction joint in concrete beam
RE: construction joint in concrete beam
If the pour ends at the bottom of the slab, make sure the surface is roughened.
BA
RE: construction joint in concrete beam
But many times those 6" high curb extensions are tough to form with flying forms and it is easier to place the curbs later, after the beam/slab has been placed.
If you can't get your ldh within the slab thickness (which you probably can't) then yes, extend the stirrups higher.
I would agree with BAretired in that as a perimeter beam we would typically use closed stirrups - a "U" shaped stirrup with standard hooks (not stirrup hooks) and a stirrup cap.
RE: construction joint in concrete beam
I'd show a construction joint between the curb and slab though with key and, if necessary, waterstop.
The goal is to cause as few pouring sessions as possible. I prefer to tell the contractor exactly where I want the construction joints on the drawings.
RE: construction joint in concrete beam