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RE: Proctor Tests
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: Proctor Tests
- From: "Sherman, William" <ShermanWC(--nospam--at)cdm.com>
- Date: Thu, 27 Jan 2005 10:52:24 -0500
I attended a seminar on soil compaction a number of years
ago - the speaker said he feels that Modified Proctor is more reliable and
should be what the industry should standardize on. But he said that currently it
is best to check with local practices/ local standards (DOT's, etc), to see what
method is most commonly used in the area or to use what the geotech recommends.
Modified Proctor compares well with heavy compaction
equipment and Standard Proctor compares well with light rollers or tamping.
Thus, Modified is often used on large civil projects and Standard is often used
for smaller projects. As Tom noted, 95% Standard Proctor is considered to
approximately relate to 90% Modified Proctor; 100% Standard Proctor is not hard
to achieve in the field but 100% Modified Proctor is much harder
One soil's report I got recommended Standard Proctor for
cohesive soils and Modified Proctor for granular soils but did not give a basis
for these recommendations.
William C. Sherman, PE
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