Block 12 HMA Volumetrics 13

HMA Volumetrics 1

Hot Mix Asphalt (HMA) Volumetric Properties

Senior/GraduateHMA Course

HMA Volumetrics 2

HMA Volumetric Terms

• Bulk specific gravity (BSG) of compacted HMA

• Maximum specific gravity

• Air voids

• Effective specific gravity of aggregate

• Voids in mineral aggregate, VMA

• Voids filled with asphalt, VFA

HMA Volumetrics 3

Volumetric Relationships

Vmb Vsb

VbaVb

Vse Vmm

Va VMA

HMA Volumetrics 4

Summary of Terms

• VMA = Voids in mineral aggregates

• Va = Air voids

• VFA = Voids filled with asphalt binder

• Gb = Specific gravity, asphalt binder

• Gse = Effective specific gravity of aggregate

• Gsb = Bulk specific gravity of aggregate

• Pbe = % by mass of effective asphalt binder

• Pb = % by mass of total asphalt binder

• Pba = % by mass of absorbed asphalt binder

• MT = Total mass

• Ms = Mass of solids

• Mb = Mass of asphalt binder

• Gmb = Specific gravity of compacted HMA

• Gmm = Maximum specific gravity of loose HMA

HMA Volumetrics 5

BSG of Compacted HMA

• Asphalt binder mixed with aggregate and compacted into a sample

Mass agg. and AC

Vol. agg., AC, air voids

Gmb =

HMA Volumetrics 6

Testing

• Mixing of asphalt and aggregate

• Compaction of sample

• Mass of dry sample

• Mass under water

• Mass saturated surface dry (SSD)

HMA Volumetrics 7

Testing

Obtain mass of dry compacted sample

HMA Volumetrics 8

Testing

Obtain mass of specimen at SSD

HMA Volumetrics 9

Calculations

• Gmb = A / ( B - C )

Where:

A = mass of dry sample

B = mass of SSD sample

C = mass of sample under water

HMA Volumetrics 10

Summary of Terms


• Va = Air voids








• MT = Total mass





HMA Volumetrics 11

Maximum Specific Gravity

Loose (uncompacted) mixture

Mass agg. and AC

Vol. agg. and AC

Gmm =

HMA Volumetrics 12

Testing

• Mixing of asphalt and aggregate• Cool to room temperature

• Mass in air• Mass under water

HMA Volumetrics 13

Testing

Loose Mix at Room Temperature

HMA Volumetrics 14

Testing

Vacuum Pump

Residual Manometer

Metal Bowl with Lid

Shaker Table

HMA Volumetrics 15

Calculations

• Gmm = A / ( A - C )

Where:

A = mass of dry sample

C = mass of sample under water

HMA Volumetrics 16

Summary of Terms


• Va = Air voids








• MT = Total mass





HMA Volumetrics 17

Percent Air Voids

Calculated using both specific gravities

Gmb

Gmm

Air voids = ( 1 - ) 100

Mass agg + AC

Vol. agg, AC, Air Voids

Mass agg + AC

Vol. agg, AC

=

Vol. agg, AC

Vol. agg, AC, Air Voids

HMA Volumetrics 18

Example Calculations

• Air voids:

• Gmb = 2.222

• Gmm = 2.423

( 1 - 2.222 / 2.423 ) 100 = 8.3 %

HMA Volumetrics 19

Effective volume = volume of solid aggregate particle + volume of surface voids not filled with asphalt

Gse =Mass, dry

Effective Specific Gravity

Effective Volume

Absorbed asphalt

Vol. of water-perm. voids not filled with asphalt

Surface Voids

Solid Agg.Particle

HMA Volumetrics 20

Effective Specific Gravity

Gse is an aggregate property

Gse = 100 - Pb

100 - Pb

Gmm Gb

HMA Volumetrics 21

Summary of Terms


• Va = Air voids








• MT = Total mass





HMA Volumetrics 22


• Mixed with 5 % asphalt cement

• Gmm = 2.535

• Gb = 1.03

100 - 5

100 - 5

2.535 1.03

Gse = = 2. 770

HMA Volumetrics 23

Voids in Mineral Aggregate

VMA is an indication of film thickness on the surface of the aggregate

VMA = 100 - Gmb Ps

Gsb

HMA Volumetrics 24


• Given that Gmb = 2.455, Ps = 95%, and Gsb = 2.703

VMA = 100 - (2.455) (95)

2.703 = 13.7

HMA Volumetrics 25

Voids Filled with Asphalt

VFA is the percent of VMA that is filled with asphalt cement

VFA = 100 xVMA - Va

VMA

HMA Volumetrics 26

Mass Relationships

Aggregate

AsphaltMb = Pb MT

Air Ma = 0

Ms = Ps MT

MT = Mb + Ms

HMA Volumetrics 27

Percent Binder Absorbed

Pba is the percent of absorbed asphalt by mass of aggregate

Pba = 100 (Gse - Gsb

Gsb Gse

) Gb

HMA Volumetrics 28

Summary of Terms


• Va = Air voids








• MT = Total mass





HMA Volumetrics 29

Effective Asphalt Content

The effective asphalt content is the total asphalt content minus the percent lost to

absorption

(based on mass of total mix).

Pbe = Pb -

Pba

100

Ps

HMA Volumetrics 30

Summary of Terms


• Va = Air voids








• MT = Total mass





HMA Volumetrics 31

Hot Mix Asphalt (HMA) Volumetric Properties

UsingPhase Diagrams

HMA Volumetrics 32

Gmb = 2.329

air

effective asphaltGb = 1.015

aggregateGsb = 2.705Gse = 2.731

absorbed asphalt

VOL (cm3 ) MASS (g)

1.000

Pb = 5% by mix

HMA Volumetrics 33

Gmb = 2.329

air



absorbed asphalt

VOL (cm3 ) MASS (g)

1.000

Ma = 0

Mm = 1.0 x 2.329 x 1.0 = 2.329

M = V x G x 1.000

Pb = 5% by mix

HMA Volumetrics 34

Gmb = 2.329

air



absorbed asphalt

VOL (cm3 ) MASS (g)

1.000

0

2.329

0.116Mb = 0.05 x 2.329 =

Ms = 2.329 - 0.116 = 2.213

Pb = 5% by mix

HMA Volumetrics 35

air



absorbed asphalt2.3291.000

0

0.116

2.213

VOL (cm3 ) MASS (g)

0.818

V =

M

G x 1.000

Vse = 2.213 = 0.810 2.731x 1.0

0.810

Vsb = 2.213 = 0.818 2.705x 1.0

HMA Volumetrics 36

air




0

0.116

2.213

VOL (cm3 ) MASS (g)

0.818

0.114

0.810

0.008

V =

M

G x 1.000

Vb = 0.116 = 0.114 1.015 x 1.0

Vba = 0.818 - 0.810 = 0.008

HMA Volumetrics 37

air




0

0.116

2.213

VOL (cm3 ) MASS (g)

0.818

0.076

0.1060.114

0.810

0.008

Vbe = 0.114 - 0.008 = 0.106

Va = 1.000 - 0.114 - 0.810 = 0.076

HMA Volumetrics 38

air




0

0.108

0.008

0.116

2.213

VOL (cm3 ) MASS (g)

0.818

0.076

0.1060.114

0.810

0.008

M = V x G x 1.000 Mbe = 0.106 x 1.015 x 1.000 = 0.108

Mba = 0.116 - 0.108 = 0.008

HMA Volumetrics 39

air




0

0.108

0.008

0.116

2.213

0.182

VOL (cm3 ) MASS (g)

0.818

0.076

0.1060.114

0.810

0.008

VMA = Vbe + Va = ( 0.106 + 0.076 ) x 100 = 18.2 %

Air Voids = 0.076 x 100 = 7.6 %

HMA Volumetrics 40

air

effective asphalt

Gb = 1.015



0

0.108

0.008

0.116

2.213

0.182

VOL (cm3 ) MASS (g)

0.818

0.076

0.1060.114

0.810

0.008

Air Voids = 7.6 %VMA = 18.2 %VFA = ( 0.106 / 0.182 ) x 100 = 58.2 %

HMA Volumetrics 41

air




0

0.108

0.008

0.116

2.213

0.182

VOL (cm3 ) MASS (g)

0.818

0.076

0.1060.114

0.810

0.008

Air Voids = 7.6 % Eff. Asp. Cont. = ( 0.108 / 2.329 ) x 100 = 4.6 %VMA = 18.2 %VFA = 58.2 %

HMA Volumetrics 42

air




0

0.108

0.008

0.116

2.213

0.182

VOL (cm3 ) MASS (g)

0.818

0.076

0.1060.114

0.810

0.008

Air Voids = 7.6% Effective Asphalt Content = 4.6%VMA = 18.2 % Abs. Asph. Cont. = ( 0.008 / 2.213 ) x 100 = 0.4%VFA = 58.2 %

HMA Volumetrics 43

air




0

0.108

0.008

0.116

2.213

0.182

VOL (cm3 ) MASS (g)

0.818

0.076

0.1060.114

0.810

0.008

Air Voids = 7.6% Max Theo Sp Grav = 2.329 = 2.521VMA = 18.2 %VFA = 58.2 %

1.000 - 0.0761.000

HMA Volumetrics 44

air




0

0.108

0.008

0.116

2.213

0.182

VOL (cm3 ) MASS (g)

0.818

0.076

0.1060.114

0.810

0.008

Air Voids = 7.6% Effective Asphalt Content = 4.6%VMA = 18.2 % Absorbed Asphalt Content = 0.4%VFA = 58.2 % Max Theo Sp Grav = 2.521

HMA Volumetrics 45

QUESTIONS ?

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Block 12 HMA Volumetrics 13

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