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what is the best way to repair this
2

what is the best way to repair this

what is the best way to repair this

(OP)
what is the best way to repair this column?

RE: what is the best way to repair this

(OP)

RE: what is the best way to repair this

According to a couple of recent threads, just encase in epoxy! Wouldn't recommend that approach!!

First, determine cause of delamination. Is it rebar exfoliation/ expansion due to corrosion? Is it freeze-thaw? Is it reactive aggregate?

Once you've determined cause of issue, you can then decide repair method.

Assuming nothing insidious, chip all loose material, dowel into column, prep exposed rebar and gouge behind for keying, provide small rebar cage outside existing, form and place new concrete. Give plenty of clearance for proper placement and embedment. Make sure new concrete is dense and will reduce permeability to protect rebar.

Obviously make sure all ok structurally!

RE: what is the best way to repair this

Thank god for confinement steel. I agree with Ron that you need to first determine the cause of the spalling. Then any fix or replacement.

Come on Ron... Epoxy would be great! hairpull

Mike McCann
MMC Engineering

RE: what is the best way to repair this

I agree with Ron and Mike.

You may need shoring. I've done some concrete repairs on bridges that turned out to be more than what they appeared to be at first.  

RE: what is the best way to repair this

Spirally reinforced columns tend to fail by spalling of the cover. Is the column heavily loaded?

BA

RE: what is the best way to repair this

(OP)
column is not heavily loaded. i'm not sure but i guess it's the rebar/ties corrosion causing spalling or maybe because it's spiraled like baretired said. i have a few of these columns but this is the most severe. this is inside an old chemical plant.

RE: what is the best way to repair this

"this is inside an old chemical plant."

What chemical?

Mike McCann
MMC Engineering

RE: what is the best way to repair this

the concrete appears to be in very poor condition, which might be explained by chemical exposure or poor consolidation or ASR? or just lots of water or humidity?
the column is very slender, bending or lateral force could cause the spalling. was there an earthquake? or did a forklift run into it?

RE: what is the best way to repair this

Personally, in looking at this closer, I would rather blow it in place.

Mike McCann
MMC Engineering

RE: what is the best way to repair this

That would be one idea, Mike...remove all concrete outside the spiral reinforcement, then wrap the thing with wire mesh and use shotcrete properly anchored to the concrete.

BA

RE: what is the best way to repair this

First thought is spalling due to porous concrete allowing corrosion of the steel. But it is hard to tell from the photos how much corrosion has occurred. The concrete looks very porous, sort of like concretes I have seen which had beach sand, shells, etc. as aggregate. I think this requires shoring, removal of cover concrete, and enclosing the column including new reinforcement.

RE: what is the best way to repair this

With hokie66 but stipulate that the cover mix be carefully selected for the particular chemical environment.

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin

RE: what is the best way to repair this

Looks like corrosion... Matter of shoring and careful hydro demolition to remove the concrete for an inch or two beyond the rebar. A cementitious patch should be applied.

Dik

RE: what is the best way to repair this

Looks like an aggregate size vs. spiral pitch issue during the original pour, the cover doesn't look like it has much aggregate. If this is the case, repair alone, is not going to cut it. I would look into additionally fiber wrapping this column in its entirety and any other columns that show similar signs of distress.

VoD

RE: what is the best way to repair this

what does the concrete inside the cage look like? Is it cracked? Loose? if it is cracked it may give an indication of ASR, DEF, or something similar. If the concrte inside the cage is fine, rebar corrosion may be more likely.

RE: what is the best way to repair this

Is the spalling cracking only on side of the column? Seems odd for corrosion, if so.

RE: what is the best way to repair this

I was going to recommend thinking about fiber wrapping, too.

RE: what is the best way to repair this

Hydro demolition will likely take care of concrete within the cage... and it may be the entire column gets removed...

Dik

RE: what is the best way to repair this

I'm with Dik,& find out what chemicals are in play so the repair can deal with them.

RE: what is the best way to repair this

Make sure that that column is vertically reinforced. Outside of a dowel at the bottom I don't see any vertical bars against the spiral. Exposé other side of column.

Send a sample of the concrete cover for chloride and petrographic analysis.

RE: what is the best way to repair this

I agree with everything already said. That column does not look healthy, and we need to know why it is spalling before giving too much advice. It does look like there is a weak plane at the narrowly-pitched spiral, under poorly-consolidated concrete cover, which may have been pushed off by corrosion products. And it was apparently formed with a cardboard tube, which is unusual for commercial, structural concrete.

You may have lost sufficient section of the spiral to justify a good washdown and installation of new confinement steel before replacing the cover. If you want to add an FRP layer for confinement, you probably need to have a smoother surface and the existing steel needs protection from further corrosion (by replacing the cover.)

RE: what is the best way to repair this

Given the time, money, and effort (and did we mention the money involved) and risk of future failure of concrete again, could he "replace" the circular concrete column with a steel hollow section arounnd the old concrete? It would require splitting the steel hollow section, putting the two halves around the concrete, and welding up both side joints; and a good foundation link or plate at the base, a good tie-in at the top, but both are needed anyway of the concrete is replaced with a thicker section by wrapping or re-concreting the outside of the current column.

A square column could work as well, which would provide a "form" to pour new concrete inside the HSS member as well if concrete is replaced.

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