CE 331
Materials II
Hot-Mix Asphalt Definitions
1. HMA Bulk Specific Gravity (Gmb) – Ratio of the weight of a unit volume of
compacted HMA mixture to the weight of an equal volume of water (includes
permeable voids as part of the volume).
2. HMA Maximum Theoretical Specific Gravity (Gmm) – Ratio of the weight of a
unit volume of uncompacted HMA mixture to the weight of an equal volume of water
(includes permeable voids as part of the volume). This value is often referred to as the
“Rice” gravity.
3. Voids in the Total Mix (VTM) – Also known as air voids. Ratio of the volume of
voids in a compacted mixture to the total compacted mixture volume.
4. Voids in the Mineral Aggregate (VMA) – Volume of voids and effective binder in a
compacted HMA mixture.
5. Voids Filled with Asphalt (VFA) – The percentage of VMA that is filled with
binder.
6. Total Binder Content (Pb) – Total amount of binder in an HMA mixture expressed
as a percent of the total mixture weight. It can also be expressed as percent of
aggregate weight.
7. Percent Binder Absorbed (Pba) – Amount of binder absorbed by the aggregate in an
HMA mixture. It is usually expressed as a percentage of the total aggregate weight.
8. Effective Binder Content (Pbe) – Total binder content less the absorbed binder
content.
9. Bulk Density – Terminology loosely used in the industry. To obtain the bulk density,
multiply the Gmb by 62.4 pcf.
Equations
Bulk Specific Gravity
G
mb
=
A
B−C
A = Dry Sample Mass
B = SSD Mass
C = Mass Under Water
Example:
Given: A=1204.6g B=1250.4g C= 759.7g
G
mb
=
1204.6
= 2.455
1250.4 − 759.7
Maximum Theoretical Specific Gravity
G
mm
=
A
A+ D− E
A = Dry Sample Mass
D = Pycnometer and Water Mass (Calibration Factor)
E = Pycnometer, Mixture, and Water Mass
Example:
Given: A=1204.6g D=7102.9g E=7833.3g
G
mm
=
1204.6
= 2.540
1204.6 + 7102.9 − 7833.3
Voids in the Total Mixture (VTM)
⎛
⎞
VTM = ⎜1 − G mb ⎟ × 100
⎜
⎟
⎝ G mm ⎠
Example:
Given: Gmm = 2.540 Gmb = 2.455
⎛ 2.455 ⎞
VTM = ⎜1 −
⎟ × 100 = 3.3%
⎝ 2.540 ⎠
Voids in the Mineral Aggregate (VMA)
⎛
⎞
VMA = ⎜100 − G mb P s ⎟
⎜
G sb ⎟⎠
⎝
Example:
Given: Gmb = 2.455 Ps=95% Gsb=2.703
(2.455 × 95 ) ⎞ = 13.7%
⎛
VMA = ⎜100 −
⎟
2.703 ⎠
⎝
Voids Filled with Asphalt (VFA)
⎛ VMA − VTM ⎞
VFA = ⎜
⎟ × 100
VMA
⎝
⎠
Example:
Given: VMA = 13.7% VTM = 3.3%
⎛ 13.7 − 3.3 ⎞
VFA = ⎜
⎟ × 100 = 75.9%
⎝ 13.7 ⎠
Percent Binder Absorbed (Pba)
⎛ G se − G sb ⎞
⎜
⎟
=
100
Pba
⎜
⎟ Gb
⎝ G sb G se ⎠
Example:
Given: Gse = 2.752 Gsb = 2.703 Gb = 1.030
P
ba
⎛ 2.752 − 2.703 ⎞
= 100⎜
⎟ × 1.030 = 0.68%
⎝ 2.703 × 2.752 ⎠
Effective Binder Content (Pbe)
P
be
= (Pb − Pba )
Example:
Given: Pb = 5.0 Pba = 0.68
P
be
= (5 − 0.68) = 4.3%