Concrete Tank Installation

[CBard]

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We are currently in the construction phase of a wastewater treatment system. We have a tank being installed that has 7 reinforced concrete sections with vertical joints. At two of the joints the contractor is unable to push it home, leaving roughly a 2 inch gap all the way around. The water depth in this tank will be approximately 7 feet. The manufacturer is acknowledging it is most likely due to cold temperatures, but claiming that because the gasket is fully seated it is a non-issue. They are proposing to finish by filling the gap with a hydraulic cement. Is there anything else I should consider and would this be common practice? Thanks.

 

[BUGGAR]

Please clarify:
Push what home?
The manufacturer of what? The concrete panels?
What does the contract say the contractor has to do?
Is this a design problem or a "field" problem?
What is the role of the "manufacturer" in this contract? Will the manufacturer "sign off and hold harmless" in this situation. Maybe even post a guarantee bond?

 

[CBard]

The male end comes with a gasket around it from the manufacturer of the concrete tank sections. The male end has been inserted into the female end to the point where the gasket is no longer visible, but the male end has not been fully pushed into the female end. The manufacturer of the concrete tanks is saying this is a field problem, but that it is a non-issue. The manufacturer provides a 1 year warranty for their tanks, and the contractor is under a 1 year warranty obligation to the owner. If the tank is leaking after one year, it will be difficult to notice and once it is noticed the owner is stuck with the problem.

 

[racookpe1978]

Show me (assume I am the owner) that a 2 inch gap is coming from low temperatures.

Hint: Multiply concrete thermal expansion coef x delta T (outside temp - daily average temp) x length of each concrete section. It will not be 2 inches, will it.

 

[JedClampett]

As my kids say, this sounds seriously cray cray.
This sounds like some kind of proprietary tank system. I've seen hundreds of tanks, and never heard of anything like this. Assuming it is round, what resists the hoop stresses? Or if it is rectangular, there's big corner stresses. If it needs a lock between sections and they don't meet up, you've got an issue.
Some prestressed tanks are made of precast walls, but those are tensioned and shotcreted after the panels are put up.

 

[CBard]

Well the two inches isn't coming from expansion, it's being assumed that with the cold temperatures the gasket is less pliant.

 

[CBard]

These are precast rectangular sections. As you can see in the picture I've attached there are tension cables that bring the sections together and hold it in place.

 

[racookpe1978]

15 Jan 15 17:02
Well the two inches isn't coming from expansion, it's being assumed that with the cold temperatures the gasket is less pliant.

Well in cold weather the concrete sections will shrink (contract) a bit, which makes the problem worse, but! - that contraction is not 2 inches. Think bridge expansion joints - they are not 2 inches in 50 feet, right?

So, what are the dimensions of this rubber gasket? 4 inches wide? 3 inches wide? Will the weather (once the project gets finished) ever get colder than it is right now?

 

[CBard]

Here's a detail of the joint and gasket. It's about a 2" wide gasket.

 

[boo1]

Looks like the gasket requires mechanical deformation to seal.
How can hydraulic cement engage the seal fingers?

 

[CBard]

I drew up a quick sketch. Left is how it should look. Right is what they're proposing to do.

 

[racookpe1978]

Scaling from the plan view of the gasket and seal joint, you can - at most! - allow only 1/2 inch (maybe 5/8 inch) gap to engage both the first and the second lips on the gasket against the second concrete surface. Anything more than 1/2 inch gap means only one lip touches the second concrete face on a flat, smooth compression-proof (leak resistant) surface.

 

[robyengIT]

Why not use material containing BENTONITE so that it will expand while wet ?

 

[bimr]

This seems to be a proprietary tank design from a concrete tank manufacturer.

You should contact the manufacturer and follow his instructions. Otherwise, you warranty will be void. Contact the engineering designer at the home office.

The manufacturer should have tolerances for this type of error.

 

[CBard]

This is the manufacturer saying that the gap isn't an issue and that they will still provide the typical warranty.

 

[zelgar]

Since everyone is saying they think the problem is that it's too cold for the gasket, has anyone tried heating the joint? I would at least require them to try having a propane heater or something onsite to blow hot air in the gap to at least attempt to get things to work properly. You would think that the tank manufacturer would have specific installation procedures for cold weather.

Also, if you were to accept the use of the hydraulic cement, I would require them to use it on both sides of the gap, not only one like you showed in your picture. Also, you might have curing problems if it's too cold.

 

[boo1]

Would filling the gap with hyd cement pack the wet side void and impact the gasket seal?

 

[cvg]

everyone seems to be convinced there is a problem, either it is too cold to install (not very likely) or that the fabrication or installation procedure is incorrect (more likely).
the drawings do not indicate that a 2 inch gap is within tolerance, so why would you accept some on the fly fix? this is a recipe for disaster. reject it outright and require correct fabrication and installation

 

[dhengr]

CBard:
Can you lubricate the bell end of the joint to help with the pressing/fitting action of the tendons? Is the outside of the tank frozen to the ground that it contacts? Is the open joint which is not visible filled with soil from the pushing/fitting process, thus preventing proper fit-up? Build a heating tent, 3'-4' on each side of the joint and completely enclosing the tank walls at the joint. Heat this for a few days to heat the concrete and to warm and soften the gasket. That should prove or disprove the manufacturer’s theory about it being to cold. I’ll bet that part of their sales pitch is that their tanks can be installed in any weather conditions. So now, put-up and shut-up Mr. manuf’er. The transfer of any loads, particularly relative lateral loads btwn. the two tank sections, any differential settlement or soil or hydraulic lateral loads, is dependant upon that joint being fully seated. Otherwise, you are trying to transfer these loads across fairly thin cantilever sections which are now much longer that the original design contemplated. Of course, water tightness is important too. If they can’t pull this together with the tendons, then get some hydraulic jacking equipment to help push on the free end of the last section.

 

[SteveWag]

I have specified many water/wastewater tanks with steel tensioning cables. I see one in the first photo. I don’t see the cable in any details. The prevention of corrosion to these cables has always been of high importance. Consider the many parking decks that have failed or have been condemned. How was/is this being done?
Steve