Specific Gravity and Absorption of Coarse Aggregate
Purpose:
To determine the specific gravity (bulk and apparent) and absorption
capacity of coarse aggregate (AGG-5)
Related Standard:
ASTM C127
Definitions:
Specific gravity is the ratio of weight in air of a unit volume of a material to the weight of
an equal volume of water.
Bulk specific gravity is the ratio of the weight in air of a unit volume of aggregate
(including the permeable and impermeable voids in the particles, but not including the
voids between the particles) to the weight of an equal volume of water.
Apparent specific gravity is the ratio of the weight in air of a unit volume of the
impermeable portion of aggregate to the weight of an equal volume of water.
Absorption is the increase in weight of aggregate due to water in the pores, but not
including water adhering to the outside surface of the particles, expressed as a percentage
of the dry weight.
Equipment: Balance, wire basket (of 3.35-mm or finer wire mesh) water tank, oven
Sample:
aggregate.
A minimum of 4000 grams (8.8 lb) test sample for both coarse and fine
Procedure:
1.
Weigh the dry test sample.
2.
Immerse the aggregate in water at room temperature for a period of 24 ± 4 h.
3.
Remove the samples from the water. Roll it in a large absorbent cloth until all
visible films of water are removed. The sample is now in saturated surface dry
(SSD) condition.
4.
Weigh the sample and obtain its saturated surface dry weight, B (g).
5.
Place the SSD sample in the wire basket and determine its weight in water: C (g).
Note that the wire basket should be immersed to a depth sufficient to cover it and
the test sample during weighing.
6.
Remove the sample from the wire basket.
7.
Calculate each type of: bulk, specific gravity and absorption.
A: Dry weight
B: SSD weight
C: Weight under water
D: As received weight
Bulk specific gravity, dry = A/(B-C)
SSD specific gravity, SSD = B/(B-C)
Apparent specific gravity = D/(D-C)
Absorption = (B-D)/D x 100
Report:
report the specific gravity and absorption values for both the blended
coarse aggregate and the fine aggregate. Explain the variations in specific gravity
between the dry, SSd and as received samples. Discuss the significance of your results
in terms of how it affects using these aggregates to make concrete.