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This video demonstrates the proper procedure for
conducting a soil density test using the
Rubber-Balloon method.
The selected test site should be smooth, level, and somewhat
larger than the volume measure device base plate.
A level surface aids in the test accuracy, because two
volume measure readings are taken at each test site.
A dozer or other construction equipment may be used to
remove the top portion of the subgrade to ensure a
representative test site.
Place the base plate over the smoothed area, and securely
fasten it down with the pins included in
the compaction kit.
The base plate must stay in place
throughout the field test.
Place the volume measure on the base plate
for the initial reading.
Once the device is in place, using the bulb-type pump, and
while holding down the volume measure, force the water down
into the balloon until resistance is felt.
Apply the calibrated pressure, and note the reading on the
glass cylinder.
After the reading is noted, reverse the bulb-type pump in
the quick coupler, and pump the water back up into the
graduated glass cylinder.
Record the reading.
This is your initial reading.
The next step in the Rubber-Balloon test procedure
is to dig a hole with a soil auger, trowel, or other tools.
The hole must be four inches in diameter and approximately
five to six inches deep to get required amount of soil needed
for the test.
Exercise care in digging the test hole, so that soil around
the top edge of the hole is not disturbed.
As demonstrated here, a hole is being dug with an auger.
An auger makes it much easier to dig through
the compacted soil.
Depth markings on the auger, such as shown here, help to
ensure the proper depth is reached.
Place all of the loose material from the hole into a
moisture-tight container.
The soil removed from the test hole will be used for weight
and moisture-content determinations.
Be careful not to lose any material.
All material from the test hole must remain within the
vertical sides of the base plate.
Clean the sides and bottom of the hole.
Check to be certain that no jagged edges or points remain
that may puncture the balloon.
With the use of a brush, sweep all fines remaining on the
base plate into the hole.
Remove the material brushed into the hole, and place it in
the container with the rest of the soil.
The wind and sun can quickly draw moisture out of the soil
removed from the test hole.
Therefore, a cover should be placed on the sample container
before proceeding with the rest of the test.
Place the volume measure back on the base plate in the same
initial position.
While holding down the device, pump the balloon down into the
hole, and apply the calibrated pressure.
Lightly tap the gauge to help stabilize the reading.
Once the final reading is noted, reverse the bulb-type
pump in the quick coupler, and pump the water back up into
the graduated glass cylinder.
Record the final reading.
Generally, earth-moving equipment is working
near the test site.
For safety reasons, it may be beneficial to move to a safer
location before completing the final steps of the test as
well as final calculations.