1Volumetric Analysis of HMA Mixtures VOLUMETRIC ANALYSIS OF HMA MIXTURES

1Volumetric Analysis of HMA Mixtures

VOLUMETRIC ANALYSIS OF HMA

MIXTURES


Volumetrics

• All matter has mass and occupies space

• Volumetrics are the relationships between mass and volume


Specific Gravity, G

Mass

Volume * w


Basic Terms• Specific Gravity (G): Gxy

– x: b = binders = stone (i.e., aggregate)m = mixture

– y: b = bulke = effectivea = apparentm = maximum

– Example:• Gmm = gravity, mixture, maximum(i.e., maximum gravity of the mixture)


Basic Terms (cont.)• Mass (P) or Volume (V) Concentration: Pxy or Vxy

– x: b = binder

s = stone (i.e., aggregate)

a = air– y: e = effective

a = absorbed– Example:

• Pb = percent binder


Volumetric Relationships

Vmb Vsb

VbaVb

Vse Vmm

Va VMA


HMA Volumetric Terms• Bulk specific gravity (Gmb) of compacted

HMA• Maximum specific gravity (Gmm)• Air voids or voids total mix (Va)• Effective specific gravity of aggregate (Gse)• Voids in mineral aggregate, VMA• Voids filled with asphalt, VFA


Gmb of Compacted HMA• AC mixed with agg. and compacted into

sampleMass agg. and AC

Vol. agg., AC, air voids

Gmb =

Vmb


Testing

• Mixing of asphalt and aggregate• Compaction of sample• Mass of dry sample• Mass under water• Mass saturated surface dry (SSD)


TestingObtain mass

of dry compacted

sample


Soak in water for 3 – 5 minutesSoak in water for 3 – 5 minutes


Testing

Obtain mass of specimen at SSD


Calculations• Gmb = A / ( B - C )

Where:

A = mass of dry sample

B = mass of SSD sample

C = mass of sample under water


Maximum Specific Gravity

Loose (uncompacted) mixture

Mass agg. and AC

Vol. agg. and AC

Gmm =

Vmm


Testing

• Mixing of asphalt and aggregate• Mass in air• Mass under water


TestingLoose Mix at

Room Temperature


Testing

Vacuum Pump

Residual Manometer

Metal Bowl with Lid

Shaker Table


Calculations• Gmm = A / ( A - C )

Where:

A = mass of dry sample

C = mass of sample under water


Air Voids

Calculated using bulk and maximum specific gravities

Air voids (Va) = 100 * Gmm – Gmb

Gmm

Vmb

Va


Why Are Air Voids Important?

• Related to Rut Resistance• Related to Durability (aging and fatigue)


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


Effective Specific Gravity

Gse is an aggregate property

Determined from a mix test

Gse = 100 - Pb

100 - Pb

Gmm Gb


Voids in Mineral Aggregate

VMA is an indication of

film thickness on the

surface of the aggregate

VMA = 100 - Gmb Ps

Gsb

Vmb

VMA


Voids Filled with Asphalt

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

VFA = 100 xVMA - Va

VMA


Percent Binder Absorbed

Pba is the percent of absorbed asphalt by wt. of aggregate

Pba = 100 (Gse - Gsb

Gse Gsb

) Gb


Effective Asphalt Content

The effective asphalt content is the total asphalt content minus the

percent lost to absorption?

Pbe = Pb -

Pba

100

Ps


Dust /Asphalt Ratio

F % passing No. 200F % passing No. 200==

AA % P% Pbebe


Factors That Influence Volumetric of HMA

• Asphalt viscosity• Mix temperature• Time held at elevated temperature


Important Considerations

• Consistent laboratory procedures– Equiviscous mixing temperatures – Mixing times

• Curing time to simulate field conditions


Example Problem


- Example Problem -

• Let’s assume we have a compacted HMA mixture with the following properties.

Bulk Specific Gravity of the Mixture - Gmb = 2.425Theoretical Maximum Specific Gravity - Gmm = 2.521Asphalt Binder Specific Gravity - Gb = 1.015Asphalt Content - Pb = 5.0 % (by mass of total mix)Percent passing No. 200 = 5.3%


- Example Problem -• Let’s also assume that three stockpiled

aggregates were used to manufacture this HMA mixture. The percent of each aggregate and the Bulk Specific Gravity (Gsb) for each is as follows:

Aggregate % of Total Aggregate G sb

2.6952.7112.721

ABC

50 %25 %25 %

-Example Problem –• Based on the information given for this problem, the

following steps should be followed:– Calculate the bulk specific gravity of the combined

aggregate– Calculate the effective specific gravity of the aggregate– Calculate the percent absorbed asphalt for the mixture– Calculate the percent effective asphalt for the mixture– Calculate the percent voids in total mix for the mixture– Calculate the percent voids in mineral aggregate for the

mixture– Calculate the percent voids filled with asphalt for the

mixture– Calculate the dust to asphalt ratio

-Example Problem –• Bulk Specific Gravity of the Combined

Aggregate - Gsb

GA GB GC

( PA + PB + PC )

PA PB PC

= 2.705

Where: PA, PB & PC = Percent by Mass of Each Aggregate in Blend GA,

GB & GC = Bulk Specific Gravity of Each Aggregate

Based on the information given:

GA = 2.695GB = 2.711GC = 2.721

PA = 50%PB = 25%PC = 25%

Gsb =

2.695 2.711 2.721

( 50+ 25 + 25 )

50 25 25 Gsb =

++ ++

++++


• Effective Specific Gravity of Aggregate - Gse

Gmm Gb

100 - Pb

100 Pb

= 2.735

Where: Pb = Percent Asphalt Binder by Total Mass of Mixture

Gmm = Theoretical Maximum SpecificGravity of Mixture

Gb = Specific Gravity of Asphalt Binder

Pb = 5.0 %Gmm = 2.521Gb = 1.015

Gse =

2.521 1.015

100- 5.0

100 5.0Gse =

--

--

-Example Problem –



• Percent Absorbed Asphalt Binder - Pba

(100 * Gb) (Gse - Gsb)

Gse * Gsb

= 0.4 %

Where: Gb = Specific Gravity of Asphalt Binder

Gse = Effective Specific Gravity of Aggregate

Gsb = Bulk Specific Gravity of Aggregate

Gb = 1.015Gse = 2.735Gsb = 2.705

Pba =

( 100 * 1.015 ) (2.735 - 2.705 )

( 2.735 * 2.705 )Pba =




• Percent Effective Asphalt Binder - Pbe

( Pba * Ps )

100Where: Pb = Percent Asphalt Binder in Total Mix

Pba = Percent Absorbed Asphalt Binder in Total MixPs = Percent Aggregate in Total Mix

Pb = 5.0 %Pba = 0.4 %Ps = 95.0 %

Pb -

= 4.6 %

Pbe =

( 0.4 * 95.0 )

1005.0 -Pbe =




• Percent Voids in Total Mix - Va

( Gmm - Gmb )

Gmm

Where: Gmm = Theoretical Maximum Specific Gravity of MixGmb = Bulk Specific Gravity of Mix

Gmm = 2.521Gmb = 2.329

= 3. 8 %

Va, % = 100 *

(2.521 - 2.425 )

2.521Va = 100 *




• Percent Voids in Mineral Aggregate - VMA

( Gmb * Ps )

Gsb

Where: Gmb = Bulk Specific Gravity of MixPs = Percent Aggregate in Total

MixGsb = Bulk Specific Gravity of Aggregate

Gmb = 2.329Ps = 95.0 %Gsb = 2.705

= 14.8

VMA, % = 100 -

( 2.425 * 95.0 )

2.705VMA = 100 -




• Percent Voids Filled with Asphalt - VFA

( VMA - Va)

VMAWhere: VMA = percent Voids in Mineral

AggregateVa = percent Voids in Total Mix

VMA = 14.8 %Va = 3.8 %

= 74 %

VFA, % = 100 *

( 14.8 - 3.8 )

14.8VFA = 100 *




Dust /Asphalt Ratio

F % passing No. 200F % passing No. 200==

AA PPbebe

Given: PGiven: P-200-200 = 5.3% = 5.3%

F 5.3F 5.3

A 4.60A 4.60== = 1.15= 1.15


Example Problem - Volumetric Equations

• SummaryGsb = 2.705Gse = 2.732Pbe , % = 4.6 %Pba , % = 0.4 %Va, % = 3.8 %VMA , % = 14.8 %VFA, % = 74 %F/A = 1.15

Volumetric Analysis of HMA Mixtures 43

Classroom Exercise


- Classroom Exercise 1 -

• Let’s assume we have a compacted HMA mixture with the following properties at 25o C.

Bulk Specific Gravity of the Mixture - Gmb = 2.413Theoretical Maximum Specific Gravity - Gmm = 2.501Asphalt Binder Specific Gravity - Gb = 1.025Asphalt Content - Pb = 4.3 % (by mass of total mix)Percent Passing No. 200 = 4.8%


- Classroom Exercise 1 -• Let’s also assume that four stockpiled aggregates

were used to manufacture this HMA mixture. The percent of each aggregate and the Bulk Specific Gravity (Gsb) for each is as follows:

Aggregate % of Total Aggregate Gsb

2.6502.6612.6752.697

ABCD

45 %15 %25 %15 %


- Classroom Exercise 1 -• Based on the information given for this problem, the

following steps should be followed:

– Calculate the Bulk Specific Gravity of the combined aggregate– Calculate the Effective Specific Gravity of the aggregate– Calculate the Percent Absorbed Asphalt for the Mixture– Calculate the Percent Effective Asphalt For the Mixture– Calculate the Percent Voids in Total Mix for the Mixture– Calculate the Percent Voids in Mineral Aggregate for the Mixture– Calculate the Percent Voids Filled with Asphalt for the Mixture– Calculate the Dust/AC Ratio


- Classroom Exercise 1 -• Bulk Specific Gravity of the Combined Aggregate - Gsb

GA GB GC GD

( PA + PB + PC + PD )

PA PB PC PD

Where: PA , PB , PC & PD = percent by mass of each aggregate in blend

GA , GB , GC & GD= Bulk Specific Gravity of each aggregate


GA = GB = GC = GD =

PA = %PB = %PC = %PD = %

Gsb =

Gsb =

++++++


- Classroom Exercise 1 -• Effective Specific Gravity of Aggregate - Gse

Gmm Gb

100-Pb

100 Pb

Where: Pb = percent asphalt binder by total mass of mixtureGmm = Theoretical Maximum Specific Gravity of mixtureGb = Specific Gravity of asphalt binder


Pb = %

Gmm = Gb =

Gse =

Gse =

--


- Classroom Exercise 1 -• Percent Absorbed Asphalt Binder - Pba

(100 * Gb) (Gse - Gsb)

Gse * Gsb

Where: Gb = Specific Gravity of asphalt binder Gse = Effective Specific Gravity of aggregateGsb = Bulk Specific Gravity of aggregate

Based on the information known:

Gb = Gse = Gsb =

Pba =

Pba =


- Classroom Exercise 1 -• Percent Effective Asphalt Binder - Pbe

( Pba * Ps )

100Where: Pb = percent asphalt binder in total mix

Pba = percent Absorbed Asphalt Binder into aggregatePs = percent aggregate in total mix


Pb = %

Pba = %

Ps = %

Pb -Pbe =

Pbe =


- Classroom Exercise 1 -• Percent Voids in Total Mix - VTM

( Gmm - Gmb )

Gmm

Where: Gmm = Theoretical Maximum Specific Gravity of mixGmb = Bulk Specific Gravity of mix


Gmm = Gmb =

Va, % = 100 *

Va =


- Classroom Exercise 1 -

• Percent Voids in Mineral Aggregate - VMA

( Gmb * Ps )

Gse

Where: Gmb = Bulk Specific Gravity of mixPs = percent aggregate in total mixGse = Effective Specific Gravity of aggregate


Gmb = Ps = %

Gse =

VMA, % = 100 -

VMA =


- Classroom Exercise 1 -• Percent Voids Filled with Asphalt - VFA

( VMA - Va)

VMA

Where: VMA = percent Voids in Mineral AggregateVa = percent Voids in Total Mix


VMA = %

Va = %

VFA, % = 100 *

VFA =


Dust /Asphalt Ratio

F F % passing No. 200% passing No. 200==AA PbePbe

P-200 = P-200 =

Pbe = Pbe =

==


F


- Classroom Problem 1 -• Summary

Gsb = Gse = Pba , % = Pbe , % = Va, % = VMA, % = VFA, % = F/A =

Volumetric Analysis of HMA Mixtures 56

Classroom Exercise 2


Classroom Exercise 3• Given

– Gmm = 2.474– Asphalt Content = 4.5 %– Bulk Sp. Gravity of Aggregate = 2.603– Bulk Sp. Gravity of Asphalt = 1.020

• Determine Gmm at 5.0, 5.5 & 6.0 %


Asphalt Content 4.5% 5.0% 5.5% 6.0%

Gmm


Questions – does it all

make sense?

Documents

1Volumetric Analysis of HMA Mixtures VOLUMETRIC ANALYSIS OF HMA MIXTURES