Humboldt H-3383L Humboldt Specific Gravity Flask (Phunque Flask) - Manual (Page 3)

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Although you may have no need for it, personnel can be familiar with the term
"apparent specific gravity," which pertains to the relative density of the solid
material making up the constituent particles (not including the pore space within
the particles that is accessible to water).
Absorption values are used to calculate the change in the mass of an aggregate
due to water absorbed in its pore spaces; as compared to the dry condition,
when the aggregate has been soaked with water long enough to satisfy most
of its absorption potential.
Bulk specific gravity is the characteristic generally used for calculations of the
volume occupied by the aggregate in various mixtures containing aggregate
including portland cement concrete, bituminous concrete, and other mixtures
that are proportioned or analyzed on an absolute volume basis. Bulk specific
gravity is also used in the computations when the aggregate is dry or assumed
to be dry.
Apparent specific gravity pertains to the relative density of the solid material
making up the constituent particles not including the pore space within the
particles that is accessible to water. This value is not widely used in construction
aggregate technology.
Absorption values are used to calculate the change in the mass of an
aggregate due to water absorbed in the pore spaces within the constituent
particles, compared to the dry condition, when it is deemed that the aggregate
has been in contact with water long enough to satisfy most of the absorption
potential. The laboratory standard for absorption is that obtained after
submerging dry aggregate for approximately 15 hours in water. Aggregates
mined from below the water table may have a higher absorption when used,
if not allowed to dry. Conversely, some aggregates when used may contain
an amount of absorbed moisture less than the 15 hours soaked condition:
For an aggregate that has been in contact with water and that has free moisture
on the particle surfaces, the percentage of free moisture can be determined
by deducting the absorption from the total moisture content determined by
T 255 drying.
When performed correctly, following the steps in this manual, the test for bulk
specific gravity and absorption level for aggregate can give accurate, repeatable
results with the Phunque Flask. By charting the results, as directed in Step 15,
technicians can track specific gravities and maintain a moving-average chart.
This way, a producer would be able to calculate volumetrics using a moving
average approach for the aggregate being used currently, rather than relying
on values determined in the past. The producer also has a repeatable test that
any member of his team can learn to perform with accurate, useful results.