Civil Engineering Reference
In-Depth Information
Weight
Volume
V
v
Air voids
Asphalt
binder
W
be
V
be
Absorbed
asphalt binder
W
s
V
s
Aggregate
FIGURE 9.26
Components of compacted asphalt
mixture.
W
t
V
t
are percent of air voids (voids in total mix) (VTM), voids in the mineral ag-
gregate (VMA), and voids filled with asphalt (VFA). These are defined as
V
v
V
m
VTM =
100
(9.1)
V
v
+
V
be
VMA =
100
(9.2)
V
m
V
be
VFA =
V
V
100
(9.3)
V
be
+
where
V
v
=
volume
of air voids
of effective asphalt binder
volume of the mixture
V
be
=
volume
V
m
=
total
The effective asphalt is the total asphalt minus the absorbed asphalt.
Sample Problem 9.2
A compacted asphalt concrete specimen contains 5% asphalt binder (Sp. Gr. 1.023)
by weight of total mix, and aggregate with a specific gravity of 2.755. The bulk density
of the specimen is
2.441 Mg/m
3
.
Ignoring absorption, compute VTM, VMA, and VFA.
Solution
Referring to Figure SP 9.2, assume
Determine mass of mix and components:
1 m
3
V
t
=
Total mass
=
1
*
2.441
=
2.441 Mg
Mass of asphalt binder
=
0.05
*
2.441
=
0.122 Mg
Mass of aggregate
=
0.95
*
2.441
=
2.319 Mg
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