VOLUMETRIC ANALYSIS OF HMA MIXTURES - Rowan...

transcript

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

MassVolume * 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 = binders = stone (i.e., aggregate)a = air

– y: e = effectivea = absorbed

– Example:• Pb = percent binder

Volumetric Relationships

Vmb Vsb

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 voidsGmb =

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 Soak in water for 3 –– 5 minutes5 minutes

Testing

Obtain mass of specimen at SSD

Calculations• Gmb = A / ( B - C )

Where:A = mass of dry sampleB = mass of SSD sampleC = mass of sample under water

Maximum Specific Gravity

Loose (uncompacted) mixtureMass agg. and AC

Vol. agg. and ACGmm =

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 sampleC = mass of sample under water

Air VoidsCalculated using bulk and maximum

specific gravities

Air voids (Va) = 100 * Gmm – Gmb

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. voidsnot filled with asphalt

Surface Voids

Solid Agg.Particle

Effective Specific Gravity

Gse is an aggregate propertyDetermined 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

Voids Filled with Asphalt

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

VFA = 100 x VMA - Va

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

Dust /Asphalt Ratio

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

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 sb2.6952.7112.721

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%

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

2.521 1.015

100- 5.0100 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

AggregateGsb = Bulk Specific Gravity of Aggregate

Gb = 1.015Gse = 2.735Gsb = 2.705

( 100 * 1.015 ) (2.735 - 2.705 )( 2.735 * 2.705 )Pba =

• Percent Effective Asphalt Binder - Pbe

( Pba * Ps )100

Where: Pb = Percent Asphalt Binder in Total MixPba = Percent Absorbed Asphalt Binder

in Total MixPs = Percent Aggregate in Total Mix

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

= 4.6 %

( 0.4 * 95.0 )1005.0 -Pbe =

• Percent Voids in Total Mix - Va

( Gmm - Gmb )Gmm

Where: Gmm = Theoretical MaximumSpecific Gravity of Mix

Gmb = 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 )2.705

VMA = 100 -

• Percent Voids Filled with Asphalt - VFA

( VMA - Va)VMA

Where: VMA = percent Voids in Mineral Aggregate

Va = percent Voids in Total Mix

VMA = 14.8 %Va = 3.8 %

= 74 %

VFA, % = 100 *

( 14.8 - 3.8 )14.8

VFA = 100 *

Dust /Asphalt Ratio

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

Given: PGiven: P--200200 = 5.3%= 5.3%

F 5.3F 5.3A 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

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 eachaggregate in blend

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

Based on the information given:GA = GB = GC = GD =

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

++++++

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

Gmm Gb

100-Pb

100 Pb

Where: Pb = percent asphalt binder by total massof mixture

Gmm = Theoretical Maximum SpecificGravity of mixture

Gb = Specific Gravity of asphalt binder

Based on the information given:Pb = %

- 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 =

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

( Pba * Ps )100

Where: Pb = percent asphalt binder in total mixPba = percent Absorbed Asphalt Binder

into aggregatePs = percent aggregate in total mix

Based on the information known:

Pb = %

Pba = %

Ps = %

Pb -Pbe =

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

( Gmm - Gmb )Gmm

Where: Gmm = Theoretical Maximum SpecificGravity of mix

Gmb = Bulk Specific Gravity of mix

Based on the information known:Gmm =

Va, % = 100 *

- 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

Based on the information known:Gmb =

Ps = %

VMA, % = 100 -

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

( VMA - Va)VMA

Where: VMA = percent Voids in Mineral Aggregate

Va = percent Voids in Total Mix

Based on the information known:VMA = %

Va = %

VFA, % = 100 *

Dust /Asphalt Ratio

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

PP--200 = 200 =

PbePbe = =

Based on the information known:

- 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%

Questions –does it all

make sense?

VOLUMETRIC ANALYSIS OF HMA MIXTURES - Rowan...

Documents