Cold Joint

[Sam1993]

Hello All:
we have about multiple concrete pours for a big area of slab foundation. How to provide a detail of Cold Joint? Are there any Typical details to show how Cold joints is done in a foundation slab and How to connect between the slabs
Thank You

 

[ALK2415]

you should design a construction-joint and there is no "cold joint" design
also you sould design a control-joints also for crack prevention .

 

[MotorCity]

Cold joint is an older term that is not very accurate. "Cold" implies a hardened concrete surface but gives no clue as to whether or not the pour was stopped intentionally.
Was it intended to be a construction joint that was planned and properly formed? Was the pour stopped midway due to an issue that needed to be remedied immediately and left a rough, jagged surface?

There are plenty of construction details out there, but I would highly recommend not using a keyed joint. They are prone to spalling and require additional labor to create the formwork.
The reinforcement (if any) should be continuous across the joint (bar couplers, lap spliced, etc.)
Also if its an environmental/water/wastewater/liquid containment structure, provide water stops at the joint.

Construction joints can also serve as control joints. However, control joints are not required in all structures (such as mat foundations and elevated slabs)

 

[Sam1993]

if they are intending to make concrete pours for the foundation slab into multiple phases due to huge area, is it better to use construction joint with dowels between the phase?

 

[milkshakelake]

Yes. You can't possibly pour a giant area in one day, and MotorCity talked about continuous reinforcement across the joint.

I'm not entirely sure how one would stick rebar out of formwork (i.e. without couplers) but I specify it on all my jobs and they get it done. With underpinning, they just stick the rebar into the soil; not sure how they do it with slabs.

 

[Lomarandil]

MSL, they drill holes in the forms (and then some concrete leaks out of the annular gap). Not the best outcome for the contractor (especially for specialty forms), but a necessary evil.

 

[ggcdn]

MSL, We usually get asked by contractors if they can use StayForm in this situation.

 

[milkshakelake]

Ah yes, that makes sense. Thanks for explaining it.