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RE: CMU in water/wastewater

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Bill,

I have looked at several wastewater plant plans and designed a few and I
have never seen CMU used in any of the tanks, even in divider walls.  Now
this in of itself does not mean that it isn't possible or hasn't been done,
but it would make me much more cautious.  Most owners expect their plants to
be usable for 50 years or more without much maintenance except for
increasing capacity.  Knowing this, I would stick to my guns with low
permeable concrete.

Also, I'm not sure how much of a cost savings you would get from using heavy
CMU grouted solid and with rebar compared to CIP walls.  Especially since
the contractor already has a concrete and rebar crew out there building the
tank walls.

Chris Towne, P.E.
Chapman Technical Group
200 Sixth Avenue
St. Albans, WV 25177
304-727-5501


On Wed, 14 Dec 2005, Sherman, William wrote:

> I have been asked to consider the use of CMU for flow divider walls in a
> wastewater basin, for cost reduction vs concrete.  My understanding is
> that CMU has been used in submerged conditions in water treatment, but
> I'm not sure about wastewater applications.  Do any others have
> experience with submerged CMU?
>
> I would assume that submergence in water actually helps keep a "moist
> cure" and prevents drying, although the top of wall would be above the
> water surface.  Anyone had any problems with the exposed portion of CMU
> due to differential moisture or due to potential freezing in a moist
> condition?  Or problems during maintenance with basins dewatered, i.e. a
> change in moisture conditions?
>
> The location in the wastewater treatment process is at a point where
> hydrogen sulfide attack is not a significant problem.  But it seems
> undesirable to allow waste materials to seep into relatively porous CMU
> vs a denser concrete, even if the CMU maintains its strength.  Any other
> thoughts on such usage?
>
>
> William C. Sherman, PE
> (Bill Sherman)
> CDM, Denver, CO
> Phone: 303-298-1311
> Fax: 303-293-8236
> email: shermanwc(--nospam--at)cdm.com
>
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