Water In Footing Holes....

fakie99

I have 5 holes dug for concrete footings that will support 30" tall 24x24" CMU/stone columns and a half-pergola (see pic). The water table is high in the area and with the footing holes excavated, 3 of them have about 8" water in 'em. I'd like to just excavate a bit further, pump out the water, then add compacted gravel to the water line and concrete from there. Obviously, frost heave is my concern. Any suggestions on just how wet an excavation can be and still do effective concrete footings?

thx

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lukachuki

don't know what code would say...but possibly something like this?

http://www.bigfootsystems.com/

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Tinstaafl

Not my field, but they do concrete pours all the time underwater, and it sets up just fine. You might want to look into that angle.

B.K

Just make sure you use a "big foot" or a pier that is tapered. Also bring down to the proper frost depth. There should be no heaving from it, even with a high water table.

For pours that are underwater, they clam the concrete always grain strength, up to 100 years. Can't says it true, but pretty interesting.

-Bill

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JDavis21835

Knowing your area, and having dug down there many times, im surprised that the banks around the hole have not slid at all. That being said, I would not worry about the water, you wont beat it down there. There are layers or silt or you are in a sandy area with a high water table. Just make sure your 4 feet deep, have the proper size holes, and fill with concrete.

As stated, concrete poured in wet conditions will eventually have more strength. The slower the cure, the stronger the set.

Chris Johnson

If you can avoid placing concrete in water I would. just before you pour, pump the water out and have a sleeve ready to go in to help hold water back. Make some up with Tyvek/Typar.

The excess water will weaken the strength of the concrete, 3000 psi concrete can be reduced to 500 psi when poured in the water with out some form of protection or block.

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Chris

MALCO.New.York

Cofferdams are for TEMPORARY Water Abatement. Once the Crete has dried and the dam removed, the water will have minuscule effect on the structure.

It is how they build Bridges!


http://en.wikipedia.org/wiki/Cofferdam

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greg24k

Depends how much water you have in there. You can put the dry concrete mix until the water is gone and blended with the dry mix, then add your regular mix.

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B.K

If you pump the water out of the holes, just before you pour, you should be in good shape. For a barrier, you could build a form (Assuming your just digging a footing and pouring concrete directly into the hole).

The concrete will have sufficient time to cure. It will be hard enough that water will not effect its strength. When the water does come back, it will be there to stay for the most part. It will act almost like flooding does for a slab, a consistent amount of water over cured concrete will only make curing time longer, and when you cure concrete for as long as possible you can achieve impressive strength.

If you don't pump the water out of the holes, and pour over that. You could be in some trouble.

We did a pour for concrete piers 10 feet deep, about 5 feet was under water, for whatever reason we were told not to pump the water out of the form, and poured it. The water rose with the concrete all the way to the top of the form, we had to take a shovel and scoop all the water off the forms, before we could float it off.

The pier came out pretty bad, there wasn't bad honeycombing, but dusting occurred, and the surface looked like somebody took a jackhammer to it, and just went banana's.

-Bill

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mrmike

I just had this problem with my holes for my Pole Barn Garage I'm building & did Exactly what you said !! It has already passed Inspection.

fakie99

well, we just pumped the water out as completely as we could, then did the pour right in the holes. thanks for the responses.

jim

thom

concrete will set up fine under water but letting the concrete fall through the water is a big no-no. The water will wash the portland cement off the aggregate and the portland will float off the top dramatically reducing the strength of the mix. The only way to make it work is to use a pump hose and keep the end of the hose below the top of the concrete as it fills up the post hole.