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This video demonstrates the procedure for conducting the
Moisture-Density Relations of In-Place soils, often referred
to as the Proctor test.
In this video, test Method A is being used to demonstrate
how to perform the test, according to AASHTO T 180.
For this procedure, each complete full Proctor test
requires a minimum of seven pounds of soil.
The sample should be approximately four percentage
points below optimum moisture.
For the first point, the soil should barely form a "cast"
when squeezed together.
To begin this test procedure, weight the empty mold without
the base plate and collar to one one-hundredth of a pound.
To prevent the soil from sticking to the base plate,
insert a paper disc in the bottom of the mold before
adding soil.
Assemble the mold and the detachable collar together and
securely fasten them to the base plate
of the Proctor hammer.
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Remix the test sample and add sufficient material to the
mold to produce a compacted layer of
approximately one inch.
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With the use of a spatula, gently level the soil surface
in the mold.
Using a manual compaction rammer or a similar device
with a two-inch face, lightly tamp the soil until it is no
longer loose or fluffy.
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Release the hammer and set it down on the soil in the mold.
Compact the soil with 25 evenly distributed blows of
the compaction rammer.
In this video the use of a mechanical rammer is
demonstrated.
The procedure used with a mechanical rammer is the same
as that of a hand-held rammer.
However, the mechanical rammer simplifies the process and
generally provides a more uniform product at a much
faster pace.
The mechanical rammer is pre-set for the correct drop
and the number of blows needed for each layer.
Once the mechanical hammer has completed the 25 blows, lift
the rammer up and lock it into place.
Following compaction of each of the first four layers, any
soil adjacent to the mold wall that has not been compacted
shall be trimmed using a spatula and evenly distributed
on top of the layer.
Remix the sample before adding soil to the mold for the
second layer.
Repeat the process of leveling the soil with a spatula, and
taking the fluff out with a hand-held rammer.
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Lower the rammer in place, and begin the 25 blows with the
compaction rammer.
This process is repeated for all five layers.
At the end of the last cycle, the top surface of the
compacted soil should be above the top rim of the mold when
the collar is removed.
After the final layer of soil is compacted, remove the mold
and detachable collar from the Proctor hammer's base plate.
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Before removing the collar, first separate the soil above
the mold using a spatula.
When removing the collar, rotate it to break the bond
between it and the soil before lifting it off the mold.
This prevents dislodging chunks of compacted soil when
lifting the collar off.
Once the collar is removed, trim the compacted soil even
with the top of the mold.
The trimming consists of many small scraping motions with a
straightedge The straightedge should be hardened steel at
least 10 inches in length.
It shall have one beveled cutting edge.
When doing the final trimming of the compacted soil, care
should be taken so no soil is removed below
the edge of the mold.
Therefore the straightedge must not be flexible, thus
preventing a concave soil surface.
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Clean all loose material from the outside of the mold and
remove the paper disk from the bottom of the sample.
Weigh the soil and the mold to the nearest one one-hundredth
pound and record.
The next step is to take a moisture sample.
With the use of an extrusion jack, remove the compacted
soil from the mold.
Using a large knife or some similar piece of equipment,
slice the plug of soil vertically down the center.
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Remove approximately 100 grams of soil from
one of the cut faces.
Take the soil for the moisture sample from the full length of
the cut face to ensure a
representative moisture sample.
Place the sample in a container that is not subject
to change in mass on repeated heating and cooling.
The container must have a close fitting lid to prevent
loss of moisture from the sample.
Weigh the sample and container immediately.
One container is needed for each moisture content
determination.
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Oven dry the sample to a constant weight, according to
AASHTO T 265 - Laboratory Determination of Moisture
Content of Soils.
Once the first point is completed, return the
remaining portion of the molded specimen to the mixing
pan and break it up.
As demonstrated here, the use of a large knife or some
similar piece of equipment generally works the best.
The material being broken up should be reduced to the size
that will pass through a number four sieve, as judged
by the eye.
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After the sample has been broken up, add it to the
remaining portion of the original sample, and
thoroughly mix the two together.
The use of a large mixer, shown here, aids in getting
the soil thoroughly mixed together.
For the second point, the moisture content in the soil
should be increased approximately one to two
percentage points over the preceding specimen.
This can be accomplished by adding approximately 60
mill-iliters of water to the soil.
And thoroughly mix the two together
to a uniform condition.
Adding that amount of water will generally raise the
moisture content of the sample to the desired percentage.
A large mixer is ideal for mixing the soil and water.
The purpose of this procedure is to increase the moisture
content in each succeeding sample until the peak density
is reached or the density decreases as
more water is added.
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