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RE: Proctor Tests

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One other bit of caution.  Be cautious of over compaction.  Often, in order to obtain the specified in-place dry density, it is necessary for the soil to be drier that it will be when it reached it's equilibrium in-situ moisture content.  When the moisture content equalizes, the soil (even non-expansive soils) has the potential to expand.  I have seen floor slabs and even building heave upward as much as 3/4".
 
Warren Foy
 
 
-----Original Message-----
From: THunt(--nospam--at)absconsulting.com [mailto:THunt(--nospam--at)absconsulting.com]
Sent: Monday, January 31, 2005 9:44 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Proctor Tests


Warren,

You are correct that I had the right philosophy but got parts of it backyards.  The grey matter just keeps on getting greyer.

Thanks,

Thomas Hunt, S.E.
ABS Consulting



"Foy, Warren" <Warren.Foy(--nospam--at)mhgrp.com>

01/31/2005 06:03 AM

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RE: Proctor Tests





I think you have it backwards.  As I recall, a standard Proctor (ASTM D698) uses a 5.5 lb hammer dropped 12"  with the sample being compacted in three lifts.  The modified Proctor (ASTM D 1557) uses a 10 lb hammer dropped 18" with the sample being compacted in 5 lifts.  The modified Proctor produces a higher compactive effort (56,000 ft-lb/ft3) than the standard Proctor (12,400 ft-lb/ft3).  (OK, I didn't recall all this, I looked it up).  The point is that a modified Proctor will produce a higher maximum density with a lower optimum moisture content than a standard Proctor.  I have heard that as a rule of thumb, 95% of a standard Proctor is close to 90% of a modified Proctor.
 
Warren Foy
-----Original Message-----
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THunt(--nospam--at)absconsulting.com [mailto:THunt(--nospam--at)absconsulting.com]
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Re: Proctor Tests


Gail,


I remember looking into this a long time ago when we called for modified proctors and received standard proctors from the lab.  As I remember, the standard proctor and the modified proctor are very similar laboratory tests with the standard proctor using more energy (a larger or heavier hammer?).  Both can be used however the desired or accepted percent compaction will be different depending on the test method.  I do not believe there is a direct correlation but if I remember right a 90% standard proctor is roughly about the same as a 95% modified proctor.  With this in mind, I seem to also remember that the standard proctor correlates better with field compaction when using very large rollers whereas the modified proctor correlates better when using smaller rollers, plate compactors, and powder-puffs.  As already suggested, best to check with a real geotech.


Thomas Hunt, S.E.

ABS Consulting



GSKWY(--nospam--at)aol.com

01/26/2005 07:47 PM

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Are there are guidelines for when you should specify a standard Proctor and when you should specify a Modified Proctor?

 
Is it  based on type or magnitude of loading?

 
 
Gail Kelley