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RE: Concrete Compression Tests

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I'll add my two cents based on trying to establish concrete strengths for
anchor testing: If you require accuracy, and not just a general idea that
your concrete strength is in the right ballpark, don't mix specimen sizes.
Uniaxial compression tests are subject to all kinds of error; changing the
specimen size just compounds the problem by increasing the effects of
lateral restraint at the specimen ends and altering the stress pattern in
general. Furthermore, the conversion factors to account for specimen
geometry vary with concrete strength.

John Silva, SE
silva(--nospam--at)hilti.com

-----Original Message-----
From: Boh Jaw Woei [mailto:boh.jaw.woei(--nospam--at)pwdcorp.com.sg]
Sent: Wednesday, January 10, 2001 08:07 PM
To: 'seaint(--nospam--at)seaint.org'
Subject: RE: Concrete Compression Tests


Using a smaller specimen would results in a higher strength recorded, and
thus need to be caution when interpreting the result. 

-----Original Message-----
From: Michael Bryson [mailto:bryson(--nospam--at)civil.ubc.ca]
Sent: Thursday, January 11, 2001 9:11 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Concrete Compression Tests



I know they've used 4x8s in Vancouver regularly for the last three or
four years.

On Wed, 10 Jan 2001, Lutz, James wrote:

> 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
> 
> 
> 
>