Hot Mix Asphalt (HMA)
Hot-Mix Asphalt (HMA)

Mixture of aggregates and asphalt binder
– Coarse aggregate
– Fine aggregate
– Asphalt binder
– Mineral Filler
Anti-strip agents,
– Additives
fiber, rubber, etc.
Hot-Mix Asphalt (HMA)

Proportioned and
mixed in a hot-mix
plant then
transported to
paving site and
placed
1
Stability

For a given
mixture, as binder
content (Pb)
decreases, air
voids increase
Stability
4
8
Air Voids, %
Durability

For a given
mixture, as binder
content (Pb)
increases, air
Durability
voids decrease
4
8
Air Voids, %
Stability vs. Durability

Design and place
HMA mixtures with
both good stability
and durability
Durability
4
Stability
8
Air Voids, %
2
HMA Volumetrics
VT
Va
Air
Ma
Vbe
Eff. Binder
Mbe
Vba
Abs. Binder Mba MT
Vs
Aggregate
Ms
Terminology

Voids in the total
mixture (VTM)
– Air voids

Voids in the
mineral aggregate
(VMA)
VT
– Volume of Pbe plus
volume of air
Va
Air
Ma
Vbe
Eff. Binder
Mbe
Vba
Abs. Binder
Mba MT
Vs
Aggregate
Ms
Terminology

Voids filled with
asphalt (VFA)
– Percent of VMA
filled with binder

Absorbed binder
content (Pba)
– Binder absorbed by
aggregate and not
available to the
mixture
VT
Va
Air
Ma
Vbe
Eff. Binder
Mbe
Vba
Abs. Binder
Mba MT
Vs
Aggregate
Ms
3
Terminology

Effective binder
content (Pbe)
– Binder available for
use by the mixture
VT
Va
Air
Ma
Vbe
Eff. Binder
Mbe
Vba
Abs. Binder
Mba MT
Vs
Aggregate
Ms
Bulk Specific Gravity of
Compacted HMA

Asphalt binder mixed with aggregate
and compacted into sample
Agg & Binder Mass
Gmb =
Vol. agg, binder, air voids
Testing
Mixing of asphalt binder and
aggregate
 Compaction of sample
 Mass of dry sample
 Mass submerged in water
 Mass saturated surface dry (SSD)

4
Testing
Obtain mass of dry
compacted sample
Testing
Obtain mass of
specimen submerged
in water
Testing
Obtain mass of
specimen at SSD
5
Calculations
Gmb
A
B C
Where:
A = mass of dry sample
B = mass of SSD sample
C = mass of sample in water
Calculating Gmb

Given:
A=1204.6 g
B= 1250.4 g
C=759.7 g
Gmb
Gmb
1204.6
1250.4 759.7
2.455
Maximum Specific Gravity
Loose (uncompacted) mixture
 No air voids

Mass agg. and binder
Gmm =
Vol. agg. and binder
6
Testing
Mixing of asphalt binder and
aggregate
 Mass in air
 Mass under water

Testing
Loose Mix at
Room
Temperature
Testing
Residual
Manometer
Metal Bowl with Lid
Vacuum Pump
Shaker Table
7
Calculations
Gmm
A
A D E
Where:
A = mass of dry sample
D = Pycnometer and water mass
E = Pycnometer, mixture, & water mass
Calculating Gmm

Given:
A=1204.6 g
D= 7102.9 g
E=7833.3 g
Gmm
Gmm
1204.6
1204.6 7102.9 7833.3
2.540
Volumetric Calculations
Gmb
Gmm
VTM
1
VMA
100
VFA
100
GmbPs
Gsb
VMA VTM
VMA
100
8
Effective Specific Gravity
Surface Voids
Gse =
Solid Agg.
Particle
Mass, dry
Effective Volume
Vol. of water-perm. voids
not filled with asphalt
Absorbed asphalt
Effective volume = volume of solid aggregate particle +
volume of surface voids not filled with asphalt
Effective Specific Gravity
Gse
100 Pb
100 Pb
Gmm Gb
Gse is an aggregate property
Example Calculations
Mixed with 5 % asphalt binder
Gmm = 2.535
 Gb = 1.03


Gse
Gse
100 5
100
5
2.535 1.03
2.770
9
Percent Binder Absorbed
• Pba is the percent of absorbed binder
by mass of aggregate
Pba
100
Gse Gsb
Gb
GsbGse
Effective Binder Content
• The effective binder content is the
total binder content minus the
percent lost to absorption (based on
mass of total mix).
Pbe
Pb
Pba
Ps
100
10