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Re: CONCRETE: Repair of Segmental Post-Tensioned Concrete Tank

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Silly me for questioning someone else's competence.  Especially someone who apparently considers himself imminently qualified to comment on anything.
 
But what then is the weird thing?  Post-tensioned tilt-up tanks?  They are not at all uncommon.
 
One might assume that being imminently qualified to comment on and evaluate something means one is very familiar with the method of construction and various options for repair.
 
But others proceed under the assumption that any idiot can do repairs.  The fact that a lot of them do generates a steady stream of income for the legal profession.
 
 
 
-----Original Message-----
From: Bill Polhemus <bill@polhemus.cc>
To: seaint(--nospam--at)seaint.org
Sent: Thu, 28 Jul 2005 11:49:57 -0500 (CDT)
Subject: CONCRETE: Repair of Segmental Post-Tensioned Concrete Tank

Hi, folks.

I have a weird one here: A Post-Tensioned tank that was done back in the
70s or thereabouts. The weird thing about it is, that it we done using
essentially tilt-up panels with ducts cast into them horizontally, then
threaded together with PT cables that were then tightened and the
anchorages (such as they were) grouted into pockets occasionally occurring
in the panels.

Then, the joints between the panels were grouted.

As you might guess, those joints are the problem: Over the years they've
continually leaked. You can see where urethane injection has been employed
numerous times (the injection ports / packers are still in place with
dried urethane oozing out of them--it's really an ugly mess).

The contractor that provides the occasional injection reports that they
cannot get any more urethane in, it just "won't go" any more.

So now the client wants alternative methods of repair. I'm on record as
saying that I believe the tank must be replaced, that repair would be
costly (probably requiring, say, a rubberized or otherwise flexible tank
liner together with, say, a new shotcrete shell--possibly requiring some
repiping.

And even then I'm not sure that the thing would last indefinitely.

Anyway, are there other repair schemes available to anyone's knowledge?
One thing to keep in mind is that I'm pretty certain the existing tank
walls need to be discounted for strength. If they're not already pretty
much "shot," it's only a matter of a short time until at least one of the
panels will "go." It's kind of a scarey situation.

Anyway, I think the client's onsite management would be quite happy to
entertain notions of replacing the tank altogether.

Comments?

Thanks in advance.


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