ASPHALT BINDERS AND ASPHALT MIXTURES - Materials for Civil and Construction Engineers - page 355

The percent voids in the mineral aggregate (VMA), is a measure of the
space available in the aggregates for the addition of the asphalt cement. The
percent VMA is the volume of the mix minus the volume of the aggregates,
divided by the volume of the mix and converted to a percent. VMA is com-
monly computed from the bulk specific gravity of the aggregate

G sb , the

bulk specific gravity of the mix G mb and the percent weight of aggregate as

P s
G sb

VMA = a 100 - G mb b (9.9)

The percent of the voids filled with asphalt, %VFA, is determined as

a VMA - VTM
VMA

VFA = 100 b (9.10)

Sample Problem 9.3

An asphalt concrete specimen has the following properties:

asphalt by total weight of mix
bulk specific gravity of the
theoretical maximum specific
bulk specific gravity of

content = 5.9 %

mix = 2.457

gravity = 2.598

aggregate = 2.692

Calculate the percents VTM, VMA, and VFA.

Solution

G mb
G mm

2.457
2.598

VTM = 100 a 1 - b = 100 a 1 - b = 5.4 %

P s
G mm

2.457 100 - 5.9
2.692

VMA = a 100 G mb b a 100 b 14.1 %

- = - =

a VMA - VTM
VMA

a 14.1

5.4

-

VFA = 100 b = 100 b = 61.7 %

14.1

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9.9.3 Superpave Mix Design

The Superpave mix-design process consists of

Selection of aggregates

■

Selection of binder

■

Determination of the design aggregate structure

■

Determination of the design binder content.

■

Evaluation of moisture susceptibility

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