Cold Joints in Columns

[2204z]

If there are cold joints in the column (for example from different concrete pours at different times (next day)).. and the cold joints are located in area of maximum moment.. what would happen to that region?

 

[hokie66]

If the joint is properly prepared, that is cleaned and normal to the column axis, there should be no great problem. But in order to prepare the joint, it would usually be necessary to remove the formwork, so cold joints in columns are best avoided.

 

[JAE]

Usual staging of concrete placement in the US is to have construction joints at the floor level (bottom of column) and at the bottom of the floor system above (top of column).

The order of placement would be:
1. Construct footings and associated footing piers, etc.
2. If the first floor is suspended, construct the floor system over the footings. Otherwise construct the column.
3. Construct the column up to the bottom of the floor/roof system above.
4. Construct the floor/roof system above.

This puts "cold" (i.e. construction) joints at either end of the column and these locations, many times, are at points of maximum moment.

In concrete construction, most construction joint strategies are to locate at or near points of maximum moment and away from points of maximum shear.
With columns, the shear is usually constant up the length while the moments are usually highest at either end.



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