ASPHALT BINDERS AND ASPHALT MIXTURES - Materials for Civil and Construction Engineers - page 354

submerged in water, a vacuum is used to remove all air from the sample. The
theoretical maximum specific gravity is

A

G mm = (9.4)

A + D - E

It is necessary to determine only the theoretical maximum specific grav-
ity of the sample at one asphalt content. However, the result should be based
on the average of three samples (with a minimum of two). By definition, the
theoretical maximum specific gravity of asphalt concrete is

100

G mm = (9.5)

a P s

P b
G b G se +

b

Solving this equation for produces G se

P s

G se = (9.6)

P b
G b

a 100

G mm -

b

where

maximum specific gravity of the asphalt concrete
weight of the aggregate
weight of the asphalt cement
specific gravity of aggregate coated with asphalt
gravity of the asphalt binder

G mm = theoretical

P s = percent

P b = percent

G se = effective

G b = specific

Although is determined for only one asphalt content, it is constant
for all asphalt contents. Thus, once is determined based on the results of
the theoretical maximum specific gravity test, it can be used in Equation 9.5
to calculate for the different asphalt contents.
The next step in the process is to determine the bulk specific gravity
(ASTM D2726) of each of the compacted specimens. This requires weighing
the sample in three conditions: dry, saturated-surface dry, and submerged.
The bulk specific gravity is computed as

G se

G se

G mm

G mb

Weight in air

G mb = (9.7)

1 2

Weight SSD - Weight in water

The unit weight of each specimen is computed by multiplying the bulk
specific gravity by the density of water, The average
bulk specific gravity and unit weight for each asphalt content are computed
and used to calculate VTM as follows:

1 Mg/m 3 62.4 lb/ft 3 1 2 .

G mb
G mm

a b

VTM = 100 1 - (9.8)