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RE: Concrete: Shrinkage limit of .048?

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Look in PCA's "Design and Control of Concrete Mixtures" (I have found this
to be one the best reference books on my shelf).  I don't believe there is a
quantitative definition of gap grading - - its basically just leaving out
certain particle sizes.  One benefit is with exposed aggregate.  Supposedly
it can be used for structural purposes, but I haven't seen that side of it.

-----Original Message-----
From: Jim Todd [mailto:JIMT(--nospam--at)performainc.com]
Sent: March 22, 2001 6:51 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Concrete: Shrinkage limit of .048?


Does anyone know a reference that defines "gap grading" vs. uniformly graded
aggregate? What would be the benefit to a mix by gap grading?

>>> SpragueHO(--nospam--at)bv.com 03/21/01 06:19PM >>>
Joyce,

Reducing water is the first step in reducing shrinkage.  Getting a different
aggregate is obviously not an option.  The aggregates in the Reno area are
volcanic in origin, and are pretty bad.

Other suggestions:
Consider a polycarbonate super plasticizer like Adva.
Use as large a maximum aggregate as possible.
Uniformly grade the aggregate.  Don't allow gap grading.
Consider shrinkage a compensating admixture like Eclipse.
Cure, cure, cure.

You won't find much help in the ACI.  

I would suggest that you contact Bud Werner at CTL Thompson in Denver
303-825-0777.

Another contact is Steve Parker in Reno.  He works for a supplier, but I
don't know which one.  Call the lab at Nevada Cement 775 575-2281.  They
will know where he is.

Regards,
Harold O. Sprague

> -----Original Message-----
> From:	Joyce Fuss [SMTP:Joyce(--nospam--at)lbdg.com] 
> Sent:	Wednesday, March 21, 2001 5:39 PM
> To:	'seaint(--nospam--at)seaint.org' 
> Subject:	RE: Concrete:  Shrinkage limit of .048?
> 
> Harold, thank you for the reply.  The location is at South Shore, Lake
> Tahoe
> (on the California side).  There are limited suppliers within a 90 minute
> range, and they have the same aggregate sources.  To import aggregate is
> not
> an option due to the tight budget (state job).
> 
> We had another project at the same campus about 7 years ago and had the
> same
> issue come up.  With a similar mix we got shrinkage in the range of .06,
> and
> had no problems with the walls, footings, beams or slabs.  These results
> are
> consistent with much of the construction of the casinos, bridges, and
> other
> structures built there.  We have the results of testing for 3000 psi
> through
> 5000 psi mixes, all with shrinkage around .06% at 21 days.  All these
> mixes
> included plasticizer.
> 
> I don't know why we have the .048 requirement in the spec, and I am
> looking
> for any type of reference as to when that would be appropriate, and what
> other limits would be recommended for various situations.  I'm not
> convinced
> it is necessary, but I don't see anything in the ACI manual of standard
> practice that gives a basis for evaluating shrinkage limits...
> > Joyce Fuss
> > Structural Engineer
> > Lionakis Beaumont Design Group
> > phone: (916)558-1900
> > fax: (916)558-1919
> > joyce(--nospam--at)lbdg.com 
> > 
>