probelems in concrete surface finish 1

[arawinda]

Hi guys, Can anybody explain the reasons for appearing concrete surfaces of columns (Grade 30) which are shown in pictures attached? Also please explain remedial actions could be taken.
Thanks....

 

[hokie66]

There may have been some issues with the concrete mix, but the main thing is total lack of compactive effort. Concrete must be compacted to achieve the required density and strength. I don't know how to fix it now.

 

[arawinda]

Thanks Hokie, But we did compaction adequately using poker and rubber hammer. You can see in picture only small area has this problem.

 

[Ron]

arawinda....looking at your second photo, it appears that the concrete was stiffening during placement. Your first photo shows a lack of consolidation at the surface, likely because of insufficient vibration for the lowering slump of the concrete during placement. It appears to be relatively minor.

The first thing you need to do is determine how deep it goes into the column. If more than a superficial depth, you have an issue that will require more extensive repair. If only superficial, then a high quality repair mortar can be used to repair the blemish.

 

[hokie66]

That looks like a very congested column, reinforcement wise. Why so many small bars in addition to the big bars? Looks like the designer was trying to create a steel column, with a bit of concrete dividing the bars. I don't think the rubber hammer helped much.

 

[Ron]

hokie66.... Yep!

 

[arawinda]

Hey Hokie , See picture attached for rf details of particular column... It is at 3rd floor level of 28 stories building. Is it steel congested?? I think there is sufficient space for aggregate movement and vibration.

 

[hokie66]

I agree that the column section you posted should provide adequate space. But the photo at the column top looks a lot different, with different size bars and more of them. In addition, the reinforcement is not centred, so the cover on one side is compromised.

 

[TehMightyEngineer]

I'll second Ron's advice. You have a pretty extensive amount of "bugholes" caused by trapped air that wasn't vibrated free. This can sometimes extend throughout the concrete and typically requires replacement of the concrete. However, I'm thinking you'll find that this is a surface issue and can be fixed with a repair mortar coating.

Looks like you also have a little bit of scaling near the top of the concrete pour. Chip away any loose concrete flakes and replace with the repair mortar.

Professional and Structural Engineer (ME, NH)
American Concrete Industries

http://www.americanconcrete.com

 

[bigmig]

Check out ACI 309R, "Guide for the Consolidation of Concrete".

Honeycombing repair procedures can be found on the net. This involves drilling and injecting epoxy, followed by
things like Xypex patch and plug systems.

Xypex would be a good place to start.