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RE: breaking concrete

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Per ACI 318, f'c is the average of two compressive tests tested at 28 days.  Any earlier test results are only for the benefit of the contractor of engineer in determining an approximate prediction of the 28 day test result.

 
 
	 Warren S. Foy, P.E.
Structural Design Manager
The Mason & Hanger Group Inc.

  _____  

300 West Vine Street, Suite 1300
Lexington, KY 40507-1814
v 859.252.9980 x221
fax: 859.389.8870
web: http://www.mhgrp.com <http://www.mhgrp.com/>  



-----Original Message-----
From: kg [mailto:firstluff(--nospam--at)oregontrail.net]
Sent: Saturday, May 25, 2002 9:36 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: breaking concrete



	Without quoting verse from ACI, in a nutshell tests are run with four
cylinders (sometimes 5 if requested). All cylinders need to go into a "wet
room" or water tank within 48 hours of casting (we try to get them within
24). The first break is at seven days, and may be up to 80% of max. testing
strength. The next two are broken at 28 days, and if all breaks are meeting
spec's, the last one (or two) are also tested. If by chance the break
strengths are low, save the last cylinder(s) for a 56 (58? right in that
area, I think 56) day break. We do not remove test cylinders from water tank
until just before we test, in fact, if we have to pull cylinders for one
reason or another before we are ready to break them (say a one hour time
limit) we cover them with wet burlap. Please if someone else has heard other
than this let me know. WE try to follow ACI standards as close as possible,
and this is our method in the lab.
	Hope this helps, and hope that this posts, first time trying this. Best to
you, Kent Golding. Kleinfelder, Bend, Or.


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