Humboldt H-3750.5F Relative Density Apparatus - Manual (Page 4)

Dry the soil sample in an oven at a temperature of 230 ± 9 F (110 ± 5C). Process
the soil through a sieve with openings sufficiently small to break up all weakly
cemented soil particles.
Minimum Density Procedure
Determine the minimum density (zero relative density), (maximum void ratio) as
follows:
a) Select the pouring device and mold according to the maximum size of
particle as indicated on the chart in Sample section. Weigh the mold and
record the weight. Use oven dried soil.
b) Place soil containing particles smaller than 3/8 inch as loosely as possible in
the mold by pouring the soil from the spout in a steady stream while at the
same time adjusting the height of the spout so that the free fall of the soil is 1
inch. At the same time, move the pouring device in a spiral motion from the
outside toward the center to form a soil layer of uniform thickness without
segregation. Fill the mold approximately 1 inch above the top and screed
off the excess soil level with the top by making one continuous pass with
the steel straight-edge. If all excess material is not removed, an additional
continuous pass shall be made but great care must be exercised during the
entire pouring and trimming operation to avoid jarring the mold.
c) Place soil containing particles larger than 3/8 inch by means of a large scoop
(or shovel), hold as close as possible to and just above the soil surface to
cause the material to slide rather than fall onto the previously placed soil.
If necessary, hold large particles back by hand to prevent them from rolling
off the scoop. Fill the mold to overflowing but not more than 1 inch above
the top. With the use of the steel straightedge (and the fingers when
needed), level the surface of the soil with the top of the measure in such
a way that any slight projections of the larger particles above the top of
the mold shall approximately balance the larger voids in the surface below
the top of the mold.
d) Weigh the mold and soil and record the weight.
Maximum Density Procedure
Determine the maximum density (100 percent relative density, minimum void
ratio) by either the dry or wet method as follows:
a) Dry Method:
1 Mix the sample of oven dried soil to provide an even distribution of particle
sizes with as little segregation as possible.