Cold Joint Seal 3

[Ogrork1]

I'm designing a 6 inch thick 6'x4'x7'deep concrete structure to hold water. The structure will be burried into the ground with only 6 inches sticking out of the ground. Construction will be pouring the slab first, then pouring the walls, creating a cold joint. Will this cold joint leak a lot of water if any at all? and if so, how do i seal this cold joint?

 

[cvg]

waterstops

 

[Ogrork1]

So I should use something like a hydrophilic water stop and polyurethane caulk to seal these cold joints? Is the sealant required in slab cold joints as well just due to rain entering and rusting the rebar? And how do they do this for swimming pools, which seem to have no waterstops?

 

[JedClampett]

You need waterstops, as cvg said. And you'll need to increase the thickness of that wall. No way you're going to get waterstops in a 6 inch wall. I've seen details for 8 inch walls, but I would go 12 inches thick. Don't rely on the soil to resist the water pressure, either. It's bad practice.

 

[cvg]

I would recommend 6 inch wide ribbed pvc waterstop.

 

[Ogrork1]

At my house, I have a 4 inch thick concrete curb shaped like a U that carries water from the creek to my back yard. That doesnt seem to leak at all. How did the previous owner manage to construct that without any waterstops?

 

[JAE]

A small channel doesn't have the same pressure from the head of water so the joint may have sealed enough to prevent water squirting through.

For a larger box, with higher water level, you might have more of a leaking problem.

Don't use hydrophilic waterstops on narrow walls as the expansion of the waterstop might blow off the concrete along the edge.

 

[cvg]

how do you know it doesn't leak? Have you looked underneath the slab to see if the subgrade gets wet? I would almost guarantee, there is a very small amount of leakage, but the risk is low so who cares?

 

[Ogrork1]

The concrete ditch is mostly above ground. I wouldnt be able to tell if its leaking a small amount along the very bottom, but along the cold joint or anywhere visible there is no leaks at all. I've ran this ditch for 24 hours once with around 4 inches of water with no noticeable leaks.

Also, were major concrete dams like the hoover dam constructed using water stops at construction joints? It doesnt seem to leak much if any at all from what I recall.

 

[cvg]

4" of water is 0.14 psi, too low to create any significant leaks

all dams leak, seepage through dams is a major issue, Hoover Dam included. First major use of rubber waterstops was on Hoover Dam.

http://www.slideshare.net/idealsolutions/waterstop-presentation

 

[JedClampett]

Ogrork1, why are you fighting us? You're not building Hoover Dam, you're building a wall that you don't want to leak. If there was a way to do it without waterstop, we'd know about it.
They build dams out of dirt and rock, but you wouldn't build a swimming pool out of that.

 

[dhengr]

While the water stop detail may call for 10 or 12" walls to be done right, on a small tank like that, those wall thicknesses sound crazy. Furthermore, that tank is all corners and no length of straight run, a further complication. Aren’t corners and joints the difficult details for water stops? Why not cast what you need for structure, and take JedC’s advice on water pressure vs. soil resistance, in doing so. Then ask a swimming pool company to line it for you. 6" sticking out of the ground could mean contaminated water from time to time.

 

[Ogrork1]

JedC, I'm not trying to fight, and sorry if it seems that way. Just trying to find out why we do certain things. For example, where I work, I see structures cast with 3 inch thick concrete, in good shape, and have been there since before anyone working here was even born. Now the same structure, most engineers in my office would use double curtain 12 inch thick walls. Also, today I just went out to the field and saw a concrete box, larger than the one I am trying to design made of 6 inch thick concrete. That structure looked very old and still in use and seems to work well.

And thanks cvg for that link. It was really helpful. I think I'll be using the rubber waterstop on the water side of the rebar to protect both from leakage and the rebar from rust. I do have a question on the hydrophilic waterstop though. If I made a 10 inch thick wall with double curtain, and placed the hydrophilic waterstop in between the rebars as the pictures in that power point imply, wouldnt that push the gap to become even larger and cause the rebar to rust?

 

[Ron]

You're going to have to dig a hole for the structure. Why not cast the structure above grade, waterproof it with proper membrane waterproofing, then lower it into the ground and backfill around it? This will keep the wall thicknesses reasonable and will give greater assurance of waterproofing.

 

[shobroco]

Where I come from, a phone call will have one delivered with a lid, guaranteed to be waterproof, and the truck will set it in the hole that you have dug before he got there. Whatever fittings you want for water in or out are cast in place & won't leak either. All of the above will be done for about 25% of what it will cost you to build your own and take 5 minutes on the phone.