Pouring concrete under water

[MossRoad]

If he uses a pipe to fill the hole with concrete, how's he going to get the post into the hole afterwards? :confused3: You ever see anyone put the concrete in the hole before the post? This is for a birdhouse. Just stick the post in the hole full of water, mix up your concrete in a 5 gallon bucket or a wheelbarrow as normal and put it in the hole around the post. Its heavier than water. It will sink right down well before it gets enough dilution to make a difference. All the excess water will come to the top and spill out around the ground. Don't over think it. Its not like you have to be concerned about structural strength on a house or building.... its just a duck house on a post!

 

[MossRoad]

From cement.org

"Will concrete harden under water?

Portland cement is a hydraulic cement which means that it sets and hardens due to a chemical reaction with water. Consequently, it will harden under water."

FAQs

 

[eray1066]

If I put a sono tube in the hole it will just be full of water also. Wouldn't I have to try to pump the water out of the tube.

Perhaps the first little bit of concrete could get wet from the water but once it is above the water in the sauna tube you can just move the sono tube loaded with concrete which will displace the water away. The trick is to get the well mixed concrete to the bottom to displace the water up Is we use this technique a lot in submerged footings

 

[Ford850]

Ha, I missed the part that this is for a duck box. OP, I thought you meant it was a duck house, as in chicken coop, and you were putting in piers for it to sit on. The tremie method would still work if you have a large enough hole for a pipe to fit in next to the duck box post, but not really necessary for setting a post IMO.
Mix the concrete, bail out as much water as you can, add the post to the hole, then fill with concrete. Even if it fills most of the way, there isn't much volume of water to disperse the concrete mix as if settles to the bottom.
The reason for the tremie is to keep the mix from separating as it falls to the bottom. If you get it in place without separating, water won't hurt anything.

 

[GPintheMitten]

In post 4 I brought up that I thought it was a box on a fence post. It doesn't need over-engineering.

But it is interesting to read all the various ideas that might help in the future for real structures.

 

[jix]

properly mixed concrete will displace the water .

Agree..Use a slightly stiff mix, pour it in on top of the water. It will displace the water as it fills the hole and harden normally and fully under water, no problem.

 

[ernieo]

To pour concrete under water use a anti washout admixture from Master Builders, Euclid Chemical, or Grace chemicals, you may be able to purchase from a local redimix producer. Usually in 5gal pails, add to concrete, it produces a film around the concrete which you can place through the water or sono tube without removing water,

you can add calcium or a concrete accelerator to speed up set times

 

[MossRoad]

Welcome to TBN!

 

[TomSeller]

If it is a just duck bird house, why even the concrete?

What kind of ducks, by the way? I have a few acres in duck ponds.

 

[lostcreekranch]

What many do here in the South is build duck houses that float, then anchor in the middle of the tank. Keeps predators away. In fact don't think I've ever heard of an elevated duck house?

Perhaps there are different strategies where you are? Your profile does not say what region you are in?

But, if this thing has to be on a pole, just mix your concrete normally and pour in the hole around your properly plumb pole / post. Nothing more, nothing less. You need no special additives. The concrete will easily displace the water.

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