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RE: Fly ash in concrete

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Here is a note from the NAVFAC Guide Specification for Cast-In-Place
Concrete which may be of value to you. You can view and possibly print the
entire specification from the CCB.Org Web page at http://www.ccb.org
<http://www.ccb.org> 
 
NOTE: Fly ash, pozzolan, and slag cement may
produce uneven discoloration of the concrete during
the early stages of construction, depending upon the
type of curing provided. Fly ash or pozzolan
meeting the specified test results, which are more
stringent than ASTM C 618, should provide acceptable
end results. Type C fly ash can be used as a
replacement for up to 40 percent of the cement.
Types F and C fly ash increase durability of
concrete. Type F fly ash and slag are replacements
for some sand and aggregates also adding to
durability.

-----Original Message-----
From: DWILLIAMSSEI(--nospam--at)aol.com [mailto:DWILLIAMSSEI(--nospam--at)aol.com]
Sent: Thursday, May 24, 2001 9:25 AM
To: seaint(--nospam--at)seaint.org
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
why. 
 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 flowability

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 2-story 
building. 

Thanks. 

David Williams, P.E. 
Snyder Engineering, Inc. 
Columbia, MO 


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