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Re: Fly ash in concrete

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Take a look at ACI 318-95 Section 4.2.3, and read the commentary.  The last
sentence states "Recent research has demonstrated that the use of fly ash,
slag, and silica fume produce concrete with a finer pore structure and,
therefore, lower permeability."

Also read the last sentence of the commentary on 4.2.1.  "...lower
water-cementitious ratios and porosity and, therefore, improved frost

Nearly all of the mix designs we review around here have fly ash in them,
and we haven't had any complaints.  It seems like adding *some* fly ash to
the mix is a good thing for your application.

Conrad Guymon, P.E.

----- Original Message -----
From: <DWILLIAMSSEI(--nospam--at)>
To: <seaint(--nospam--at)>
Sent: Thursday, May 24, 2001 10:24 AM
Subject: Fly ash in concrete

> Has anyone had negative experiences with using fly ash in concrete mixes?
> I'm working with an architect who doesn't want it used, but I'm not sure
>  The spec's call for 3,500 psi 28 day strength concrete.  Fly ash is not
> mentioned in the spec's, but a contractor has asked if it's permissible to
> add it to the mix.  I understand that fly ash is used to improve
> of dry mixes.  I couldn't find much other information regarding the use of
> fly ash in ACI 318 or any of my materials and concrete references.
> The application for the concrete in question is spread footings for steel
> columns and perimeter footings for slab/brick masonry support for a
> building.
> Thanks.
> David Williams, P.E.
> Snyder Engineering, Inc.
> Columbia, MO

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