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RE: Proctor Tests
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: Proctor Tests
- From: "Foy, Warren" <Warren.Foy(--nospam--at)mhgrp.com>
- Date: Mon, 31 Jan 2005 09:03:56 -0500
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
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
01/26/2005 07:47 PM
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?