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RE: Concrete shrinkage (was curing)

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Bill,
After it is in the mix, the only proof would be in the form of a petrographic analysis. As in any aspect of concrete mix verification, the best verification approach is independent inspection at the batch plant. Independent verification, special inspection or whatever you want to call it was more common in the past.

We (engineers in general) have drifted away from batch plant inspection in more recent years. But I have found that the practice helps avoid problems that can cost hundreds of thousands of dollars. A few years ago, I had a batch plant in Colorado's Front Range switch fly ash and cement portions. We noticed the problem when the removal of the anchor bolt templates removed the anchor bolts after 24 hours from placing. The batch plant paid for the cost of fixing the problem, but the schdule impact really hurt the project. The project would have been better served with an on-site, independent, concrete mix inspector.

Specifically to gradation, the inspection is just a sieve analysis on the stock pile that any of the labs that do concrete work should be able to do. The quarries that produce crushed rock mostly use computerized sieves now, and they should not have a problem with mixes that are not the standard C33 gradations.

Regards,
Harold Sprague


From: "Sherman, William" <ShermanWC(--nospam--at)cdm.com>
Reply-To: <seaint(--nospam--at)seaint.org>
To: seaint(--nospam--at)seaint.org
Subject: RE: Concrete shrinkage (was curing)
Date: Fri, 2 Jul 2004 19:48:57 -0400

I agree. But I am curious - what method do you use to get the concrete
supplier to provide "a uniform gradation on the coarse aggregates"?

William C. Sherman, PE
(Bill Sherman)
CDM, Denver, CO
Phone: 303-298-1311
Fax: 303-293-8236
email: shermanwc(--nospam--at)cdm.com


Harold Sprague wrote:

> Related to this is my tendency to use polycarbonate
> superplasticizers and a uniform gradation on the coarse
> aggregates.  This is to minimize cement and minimize water.
> The less paste in a mix, the better.  The aggregates do not
> shrink.  Reactive aggregates are another story.

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