Testing for a horizontal cold joint in a ground floor slab pour? 1

[abusementpark]

How would go about testing to see if a horizontal cold joint formed in a ground floor slab pour? You suspect a cold joint formed because a portion of the slab was poured in two horizontal layers and the time elapsed between pours was questionable.

I assume you would start with taking some cores. But what would tests would you perform if the cold joint is inconclusive from visual inspection of the cores?

 

[Ron]

Cross-section the cores through the thickness of the slab. Cold joint will be obvious from aggregate pattern, even if bond occurred.

 

[abusementpark]

Cross-section the cores through the thickness of the slab. Cold joint will be obvious from aggregate pattern, even if bond occurred.

I see. But couldn't there be a situation where there is a gray area (no pun intended)?

 

[emmgjld]

Sonic Testing will pick up these kinds of discontinuities.

 

[charliealphabravo]

You could try manually sounding the slab by dragging a chain across it. I think the DOT's use that method. If the cold joint is localized you might hear the change.

 

[msquared48]

It's a cold, hard fact, though, that the steel chain needs to be cold to detect the cold joint.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[charliealphabravo]

 

[Ron]

abusementpark....low frequency ultrasonics will pick up true delamination from a cold joint; however, it will not pick up if there is some level of bond continuity that could be problematic later. That's why I prefer the visual assessment by cross-sectioning and polishing the specimen so that I can detect the paste integrity, aggregate striations, and potential separation along the paste line.

Chain dragging is effective for delamination, but has the same limitation as the ultrasonic.