Civil Engineering Reference
In-Depth Information
At present, there is no standard method for determining the effective spe-
cific gravity of aggregates directly. The U.S. Corps of Engineers has defined a
method for determining the effective specific gravity of aggregates that absorb
more than 2.5% water.
The specific gravity and absorption of coarse aggregates are determined
in accordance with ASTM C127. In this procedure, a representative sample
of the aggregate is soaked for 24 hours and weighed suspended in water. The
sample is then dried to the SSD condition and weighed. Finally, the sample
is dried to a constant weight and weighed. The specific gravity and absorp-
tion are determined by
A
Bulk Dry Sp. Gr. =
(5.5)
B
-
C
B
Bulk SSD Sp. Gr. =
(5.6)
B
-
C
A
Apparent Sp. Gr. =
(5.7)
A
-
C
B
-
A
Absorption
1
%
2
=
1
100
2
(5.8)
A
where
A
=
dry weight
B
=
SSD weight
C
=
submerged weight
ASTM C128 defines the procedure for determining the specific gravity
and absorption of fine aggregates. A representative sample is soaked in
water for 24 hours and dried back to the SSD condition. A 500-g sample of
the SSD material is placed in a
pycnometer,
a constant volume flask; water
is added to the constant volume mark on the pycnometer and the weight is
determined again. The sample is then dried and the weight is determined.
The specific gravity and absorption are determined by
A
Bulk Dry Sp. Gr. =
(5.9)
B
+
S
-
C
S
Bulk SSD Sp. Gr. =
(5.10)
B
+
S
-
C
A
Apparent Sp. Gr. =
(5.11)
B
+
A
-
C
S
-
A
Absorption
1
%
2
=
1
100
2
(5.12)
A
where
A
=
dry weight
B
=
weight
of the pycnometer filled with water
of the pycnometer filled with aggregate and water
surface—dry weight of the sample
C
=
weight
S
=
saturated
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