Use of water stop in Vertical Suspended Pump Can Foundation 1

[oengineer]

Is it beneficial to use a water stop between the bottom slab & the wall of a Vertical Suspended Pump Can Foundation. The image below depicts what I am asking.

What are the advantages & disadvantages of providing a water stop at these locations in the foundation for the pump can?

My initial thought is that since the concrete bottom slab & wall are cast monolithically together it is not needed.

Comments/suggestion are appreciated.

 

[jayrod12]

Does the foundation need to be water tight? either from water infiltrating in from the ground, or water infiltrating the ground from inside the can?

If so, then there should be a waterstop.

 

[oengineer]

Does the foundation need to be water tight? either from water infiltrating in from the ground, or water infiltrating the ground from inside the can?

If so, then there should be a waterstop.

I do not want any water to infiltrate the pump can, so yes.

How would water be able to either infiltrate in from the ground, or infiltrate the ground from inside the can if the concrete is cast monolithically together?

Also, do you happen to have a detail oh how the water stop should be applied in this situation?

 

[jayrod12]

If cast monolithically, then no, but have you asked a contractor how they would perform that? Most around here would want to pour the bottom slab first and then the walls. That's why I said yes.

 

[oengineer]

If cast monolithically, then no, but have you asked a contractor how they would perform that? Most around here would want to pour the bottom slab first and then the walls.

I think that the contractor might pour the slab separate as well.

Do you happen to have a detail of how the water stop detail would look in this situation?

 

[jayrod12]

Often we just use either a bead of sikaswell in the shear key, or a strip of the volclay style waterstop. Not much to the detail.

My issue with the pre-formed PVC ones is they're rarely secured well enough to actually stay in place during the pour, so they end up being ineffective.

 

[JoelTXCive]

Below is the standard wall to slab interface detail that is on our plans. It is also part of the City of Houston standard lift station details (which is why we keep it on our plans)

This detail is for a 6" PVC waterstop. I've been to several 1-hr lunchtime waterstop training classes; and most people feel that that the 6" PVC waterstops when installed correctly are better performing than the Sikaswells or other hydrophilic waterstops.

BUT....As Jayrod mentioned. Waterstop likes this get messed up all the time. They get pushed out of the way by the wet concrete; or the lower 'wing' of the waterstop gets smushed down into the rebar cage.

The below detail requires that the joint be lifted 4" off the slab, but that often gets missed by inspectors or doesn't happen.

 

[oengineer]

If the contractor chooses to cast the slab & walls separately, I am under the impression that a control joint would be required.

The image below shows the way I would believe the foundation to be built, using a water stop:

Below is the standard wall to slab interface detail that is on our plans. It is also part of the City of Houston standard lift station details (which is why we keep it on our plans)

This detail is for a 6" PVC waterstop. I've been to several 1-hr lunchtime waterstop training classes; and most people feel that that the 6" PVC waterstops when installed correctly are better performing than the Sikaswells or other hydrophilic waterstops.

My concern with the detail shown from the City of Houston is that it seems to be using a Keyway to join the wall & slab. I would like to avoid the use of a keyway in this situation. I would like to have the wall & slab join together when cast, but with while still using the water stop.

 

[GC_Hopi]

What kind of formwork would allow you to pour the slab and wall monolithically?

 

[oengineer]

What kind of formwork would allow you to pour the slab and wall monolithically?

I am not sure of the means & methods for the contractor of how they would construct both the slab & wall together.

 

[dik]

I like using bentonite 'rod', myself. I've had problems with using plastic strips. It's common to see a joint raised off the slab, but I don't like that either.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[JedClampett]

We do a lot of these. A lot.
[li]We pour a concrete slab.[/li]
[li]Mount the pump can that is welded to a base plate larger than the can.[/li]
[li]Level the pump can using anchor bolts and non shrink grout.[/li]
[li]Encase the can in concrete to grade.[/li]
No waterstop as the water is totally contained in the pipe and base plate.

 

[JoelTXCive]

OEngineer-

I think the keyway can be deleted too. I have been way down the rabbit hole on shear friction research for retaining walls; and as a result, I am a big believer in it. In my opinion; at a wall to slab interface; no keyways are needed.

But........I think contractors + inspectors are used to keyways and expect to see them. Almost every time I leave them off the plans, I get an RFI or a phone call from the field wanting to know "where is the keyway" I have given into peer pressure and continue to show them on the plans; especially city plans where city inspectors will be looking at them.

The 4" raised joint is necessary though to keep the waterstop out of your slab rebar. If the slab rebar has 2" cover and you have a waterstop with a 3" 'wing', then the waterstop will be touching your rebar. You have to lift the joint to provide clearance for the waterstop.

If you want a totally flat joint, then the hydrophilic waterstops are the way to go.

 

[phamENG]

What are the dimension on that thing? Looks to be 18" thick walls with about a 2' diameter space in the middle. Seems like a whole lot of concrete.

It's not a control joint, it's a construction joint. Control joint refers to a joint intended to control cracking. A construction joint is a spot where the contractor can stop pouring, let the first pour set up, and then start pouring again. The PVC bell type water stops are great if they're installed correctly. The bentonite strips are good, too, but they need to be secured in place. It's easy for them to get knocked loose when pouring the walls and then they're pretty worthless.

The means and methods used in construction may ultimately be the responsibility of the contractor, but we have a responsibility to make sure there is at least one method to accomplish it when we design it.

 

[GC_Hopi]

oengineer: As the engineer you need to consider constructability. If you give some thought to what you are asking you may realize that having a construction joint at the slab to wall interface is the best approach and what you propose is costly and difficult to construct which adds unnecessary cost to the owner.

 

[dik]

I didn't realise the void was filled with concrete... just make a concrete box, no keyway no waterbar.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dauwerda]

Aren't these things essentially a drilled pier? Drill the hole, form the top, drop in the rebar cage, drop the steel casing in the middle, then fill the annular space with concrete.

 

[oengineer]

We do a lot of these. A lot.
We pour a concrete slab.
Mount the pump can that is welded to a base plate larger than the can.
Level the pump can using anchor bolts and non shrink grout.
Encase the can in concrete to grade.

No waterstop as the water is totally contained in the pipe and base plate.

Although the images I show both have pipe cans which contain the pump, a can will not be provided for this pump foundation. I am not sure if it will be provided by the vendor, but our structural drawing will not include based on suggestions provided by the pump vendor.

If pipe cans are not provided, should a waterstop be included in the foundation?

 

[AskTooMuch]

What dauwerda said is similar to the goby I have from a large EPC company for vertical pump except it didn't even have any rebar.

Drilled shaft with standard pipe (with welded studs) inside. 6" cover from each side of pipe and the bottom.

What's the point of the thick concrete with lots of reinforcement?

 

[JedClampett]

If pipe cans are not provided, should a waterstop be included in the foundation?

I guess in that case I'd put in a waterstop, but I can't imagine a pump supplier who would trust the operation of their pump to a concrete caster. I think they like the tolerances they can obtain from a steel pipe.