Horizontal Column Cracks During Curing 7

[YuleMsee]

What went wrong here, column ain't loaded yet, just cured. Its A 600mm DIA. column, 8D20 bars, D8 links @ 225mm spacing concrete class 25.

 

[dauwerda]

@oldestguy @JLNJ, yes they were done with wheel barrows, what is the connection between how concrete is transported and the cracks?

I believe they were getting at the idea that the cracks may be cold joints due to the concrete being placed in small increments as opposed to one continuous pour.

 

[oldestguy]

hoki66 and the rest: Hey, the poster disagrees.
The root cause for the cracks is inadequate consolidation. Was the concrete in these columns vibrated at all?

He says vibration was done. Blame it on the wheelbarrow batches.

 

[hokie66]

oldestguy,

Initial vibration is not enough to prevent plastic settlement cracks. In deep members like deep footings or pile caps with top reinforcement, you will often get plastic settlement cracks over the bars even with good concrete consistency. The only way to prevent these in the finished structural element is to revibrate.

Revibration in columns is not very practical, so compaction needs to be done well the first time, and that was hot done here. Just sticking a poker in the column for a few seconds is not the same as adequate compaction. Wheelbarrows, bah!

 

[r13]

I wonder what is the outcome by vibrating sand and gravel mix, that with a lot of water albeit there is some cement.

 

[hokie66]

The OP did. You took his word about vibration, why not about reinforcement?

 

[oldestguy]

OG deleted his post when corrected by hokie66