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Large voids in concrete column

Large voids in concrete column

Large voids in concrete column


Today I noticed a large void (100mmx150mm) in one of the columns at my site, this is a 6m high battered column and the hole merged out of nowhere. The column was poured approx 6-7 months ago. I asked the guys to chip out the concrete and expose the void in its entirety and its about 100mm deep as well. I would like to to how serious of a concern this is and whether a Sika non shrinkable high strength grout after applying concrete adhesive is a proper solution?


RE: Large voids in concrete column

I'd be concerened with how that void happened? How many there are in the placement? the cracking below the opening does bring up more concern.

I'd say the EOR should be contacted. if that is you, then you should figure out how it happened? where else it is (maybe a thermal camera)? Do you need that rebar and column?

RE: Large voids in concrete column

If it is just that one void, you can just fill it with a concrete repair mortar. Not a grout, and not with adhesive.

But like Eric, I would want to know how it happened, and if the problem is more extensive.

RE: Large voids in concrete column

Agree with Hokie. I'd want to better understand how / why it happened. Maybe this would indicate it's time to spend some time on some GPR / non-destructive testing to see if it can find any more voids like this. Not just in this column, but a representative number of columns subject to the same mix and construction methods that led to this void.

RE: Large voids in concrete column

Other than the surface material that came off, was the inside a true void or was there loose material inside that also fell out? If it is a true void, I have never seen one that "clean" looking.

RE: Large voids in concrete column

I've seen them that clean looking but not something that clean and that big. Agreed with Ron, that should have jagged edges with rough aggregate showing unless there was something that was physically in that void that was removed prior to the photo being taken.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)

RE: Large voids in concrete column

All, just an update to everyone: The contractor has cleaned up the two areas and chipped the loose concrete to sound concrete. See picture below

RE: Large voids in concrete column

The original post only mentioned one place. Did you find the 2nd one while chipping the first or did you just fail to mention it in the original post? The 2nd one bothers me more than the first one because they are somewhat mirror image. How does the bar layout change where the wall to the right terminates about 7" above the defects? I assume there is some change in the rebar at this approximate area. The picture looks like a wall intersects at this location.

RE: Large voids in concrete column

Ron247 Correct! the second cavity was discovered afterwards. See the sketch below with regards to rebar layout. My concern is whether concrete mortar repair infill is a viable solution and whether the column will still be able to perform as intended by the designer. EOR is in the process of reviewing this and I thought it would be beneficial to hear other people's thoughts and ideas. Thanks

RE: Large voids in concrete column

I would really poke around below the existing defects to see if I have more under them. I would not be too worried about the defects above as much as I would be under them. If them defect is in the haunch I see for the beam, I would really review it. In your drawing, where are the defects at?

RE: Large voids in concrete column

If you can get someone to buy into it, do some ultrasonic testing of the column for more voids. Grid will have to be 4 to 6 inches but will likely find similar voids if there. Since you likely don't have any specimens of the original concrete, it will make the interpretation a bit more difficult, but if you have pervasive lack of consolidation that's a concern.

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