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RE: w/c ratio after concrete set

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I guess I've been in practice too long.  After a while, you see it all.

The statement is not entirely accurate.  The ready mix plant was not
unscrupulous, just lax.  

The ash a given power plant produces is a function of the coal supplied to
that power plant.  As reported to me on a project several years ago a coal
fired power plant switched coal suppliers, and the previous ash was from
bituminous coal and produced F ash.  The power plants are looking for the
most economical cost of energy.  Fly ash is simply a byproduct.    The new
coal was subbituminous and produced C ash.  Somehow the stock piles got
mixed up, and the ash supplied to the ready mix plant was a C not the
specified F.  The paper work stated the ash was F.

For the particular application it was not a big deal.  If sulfate resistance
was in issue, it would have been a big deal.

In my statement, I was being generic.  It is possible to mix up fly ash at
any step.  That is why we test stock piles at the ready mix plant.

I had one occasion where the cement and flyash were mixed up.  After 24
hours the concrete had not set.  That one was ugly.

Harold Sprague

> -----Original Message-----
> From:	Roger Davis [SMTP:rdavis(--nospam--at)]
> Sent:	Wednesday, July 19, 2000 4:34 PM
> To:	seaint(--nospam--at)
> Subject:	RE: w/c ratio after concrete set
> Harold, is this statement correct?
> "An unscrupulous ready mix plant could also ...use type C ash in lieu of
> F..."
> Roger Davis
> SDS Architects, Inc
> 205 N. Dewey Street
> Eau Claire, WI 54703
> 715-832-1605
> rdavis(--nospam--at)
> -----Original Message-----
> From:	Sprague, Harold O. [mailto:SpragueHO(--nospam--at)]
> Sent:	Tuesday, July 18, 2000 4:52 PM
> To:	seaint(--nospam--at)
> Subject:	RE: w/c ratio after concrete set
> David,
> Petrographic tests will give a back door method to determine apparent w/c
> ratios in hardened concrete.  The best approach is sharp special
> inspectors.
> I have had rare occasions where I have had special inspectors at the plant
> and at the site to corroborate mix proportions.  It is generally not a
> problem.  If a ready mix plant is predisposed to fraud, they will commit
> fraud no matter what.
> An unscrupulous ready mix plant could also delete Durapoz, micro-silica,
> uniform graded aggregate, use type C ash in lieu of F, use ASR aggregate,
> or
> any other number of things that could not be detected by normal field
> plastic concrete tests.
> A good finisher will know either immediately or within a couple of hours
> if
> the mix was juiced (too much water) or if they used super-P.
> There are several other advantages of polycarbonate high range water
> reducers other than the ability to batch it at the plant.
> The only thing that I know for sure is that the ability to properly batch
> concrete, and do the mix submittal correctly is highly regional.  I have
> worked in areas where they add air-entraining in all concrete.  It plays
> hell for steel trowel finished concrete.  Some regions don't have a clue.
> Some regions don't have a problem.  Chicago is one of the best areas.  I
> won't get into the areas that are clueless.
> Regards,
> Harold Sprague

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