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Cold Joint in Column
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Kumar_Abhishek_Singh
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PostPosted: Wed Oct 18, 2017 9:05 am    Post subject: Reply with quote

Enclosed file/picture shows how WE do thecold joint in column (only when absolutely necessary). Additionally,

1. We design the column rings around the joint to take 100%shear...no concrete capacity taken.

2. Dowels are additional precaution. Concrete notch/shear keyis also additional precaution (you can calll it 'redundant'). Why, because if Iam forced to give a cold joint in column that means that the workmanship of thecontractor is questionable (if he cant make a 3m column in one go, what elsecan he make) and that I cant trust him with quality of steel being used etcetc...so I have my ways of saving myself.

3. Our codes need to have specific clause for this. Alas,even ACI-318 cl 6.4.3 (if my memory is right, its written in the commentary of6.4.3) doesn't give full picture. We can design for shear using shear frictiondesign method of 11.6 of ACI-318.

Hope this helps... <o></o>



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es_jayakumar
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PostPosted: Wed Oct 18, 2017 10:37 am    Post subject: Reply with quote

Abhishek ji,

This is my perpetual doubt : how new and old concretes perfectly bond at such a column / beam / slab construction joint ?

E S Jayakumar
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spsvasan
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PostPosted: Thu Oct 19, 2017 3:52 am    Post subject: cold joint in column Reply with quote

Dear SEFIans

A very useful discussion.

A joint is supposed to be a cold joint when the subsequent layer of concrete is placed against the previous layer of concrete after the initial set and before the final set of the first layer of concrete.

If the second layer is placed after the final set of the first layer of concrete, it is a construction joint.

Hence all these discussions are pertaining to construction joint in columns

Generally, axial forces and flexural forces are effectively transmitted across construction joints and cold joints. The joint can be relatively weak in shear. Hence, it is normal practice to locate all construction joints at points of minimum shear.

In that case, is there no preferred location [bottom of column, or mid point or top of column] for construction joint in column?

Good compaction near the joint is necessary. The solution given by Er.Kumar Abhishek Singh gives a positive shear transfer. But the outer ring portion and the central key portion have to be compacted properly.

In several sites coarse aggregates are pressed into the top of fresh column concrete such that they are half buried and half protruding. This also appears to have a reasonably good  shear transfer.

Dear Er.Jayakumar

This is my perpetual doubt : how new and old concretes perfectly bond at such a column / beam / slab construction joint ?


Could this be due to continuing hydration on both sides of the joint?

S.P.Srinivasan
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shefypattambi
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PostPosted: Thu Oct 19, 2017 4:34 am    Post subject: Reply with quote

Dear
S.P.Srinivasan Sir,
Thank you for such detailed explanation.
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