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RE: Concrete Compression Tests

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Jim,

I believe that the ASTM spec (ASTM C 31) states the "standard" is 6 x 12
unless dictated differently by the project specifications.  The real issue
here is to make sure you're not testing the "aggregate" when you should be
testing the complete mix.  ASTM C 31 even mentions that for the 6 x 12
cylinder that if the maximum size aggregrate in the mix is over 2" then the
diameter of the cylinder should be 3 times the maximum aggregate size or the
mix should be wet sieved.  Most mix design's that I've approved usually
contain a maximum aggregate size of 1.5" thus using the ASTM standard as a
baseline that would make for a minimum diameter of 4.5" for the cylinder.
Hope this helps.....

Robert C. Rogers, PE
robert.rogers(--nospam--at)woolpert.com

Woolpert LLP
Ph:   937-341-9417
Fax: 937-461-0743


-----Original Message-----
From: Lutz, James [mailto:JLUTZ(--nospam--at)earthtech.com]
Sent: Wednesday, January 10, 2001 4:30 PM
To: seaint(--nospam--at)seaint.org
Subject: Concrete Compression Tests


The ASTM default standard for compression test cylinder molds (for
acceptance testing) has been 6 inch diameter x 12 inches for as long as I
can remember, but the test labs tell me that about half the tests they run
these days are on 4 inch diameter x 8 inch specimens. Has anybody out there
had problems with the reliability of the tests done with the smaller
specimen size. The tests are a little cheaper with the smaller size, and I'm
getting asked if it's ok to use them.I don't know whether I should go with
the flow or insist on the old standby.

Jim Lutz
Earth Tech, Inc.

10800 NE 8th Street - 7th Floor
Bellevue, WA 98004
(425) 455-9494
(425) 453-9470 FAX