selecting the correct pg asphalt for your airport project 29 th annual faa airports conference...

Selecting the Correct PG Asphalt Selecting the Correct PG Asphalt for Your Airport Projectfor Your Airport Project

2929thth Annual FAA Airports Conference Annual FAA Airports ConferenceHershey, PAHershey, PA

March 2, 2006March 2, 2006

Ronald CorunRonald CorunCITGO Asphalt Technical Support ManagerCITGO Asphalt Technical Support Manager

A Driving Force In Asphalt

What is SUPERPAVE?What is SUPERPAVE?

New Asphalt Binder New Asphalt Binder specificationspecification

New Mix Design procedure New Mix Design procedure using a new laboratory using a new laboratory compaction devicecompaction device

We Have Three Asphalt We Have Three Asphalt BindersBinders

Q.Q. How do we determine which asphalt How do we determine which asphalt binder is best for our project?binder is best for our project?

A.A. The asphalt binder that gives the best The asphalt binder that gives the best performanceperformance

A B C

Performance ?Performance ?

Q.Q. What areas of poor performance do we want What areas of poor performance do we want to avoid ?to avoid ?

Or, in other words, how do our Or, in other words, how do our asphalt pavements asphalt pavements failfail ? ?

?

How do asphalt pavements How do asphalt pavements fail ?fail ?

SP

How Did We Measure Asphalt How Did We Measure Asphalt Properties Before the PG Properties Before the PG

Grading System?Grading System?

Penetration Grading Penetration Grading Viscosity GradingViscosity Grading

100 g100 g100 g100 g

penetrationpenetration

0 sec0 sec5 sec5 sec

PenetrationPenetrationViscosityViscosity

vacuumvacuum

25° C25° C 25° C25° C

60° C60° C

Problem with Problem with one temperature gradingone temperature grading

HARD

SOFT

60°C25°C

A

BC

A

C

B

PEN VISC

Problem with Problem with one temperature gradingone temperature grading

According to the Penetration system:According to the Penetration system:

According to theAccording to theViscosity System:Viscosity System:

HARD

SOFT

60°C25°C

A

BC

A

C

B

PEN VISCA C=

B C=

Asphalt bindersAsphalt binders

Q.Q. Are the properties of asphalt binders Are the properties of asphalt binders constant over a pavements performance constant over a pavements performance life? life?

A.A. NO! An asphalt binder’s response NO! An asphalt binder’s response to loading is a function of to loading is a function of three factors. . . three factors. . . AgeAge TemperatureTemperature Rate of LoadingRate of Loading

?

Asphalt binder’s response to Asphalt binder’s response to loading is a function of. . .loading is a function of. . .

1. age

AgingAging

Asphalt binders undergo aging through Asphalt binders undergo aging through the loss of volatiles the loss of volatiles (a.k.a. loss of light (a.k.a. loss of light ends) ends) and oxidation.and oxidation.

From the standpoint of determining an From the standpoint of determining an asphalt binder's performance there are asphalt binder's performance there are three key ages we need to address.three key ages we need to address.

?

Key AgingKey Aging?

New material - no agingNew material - no aging

During constructionDuring construction Aging in the plantAging in the plant Aging during placementAging during placement

Late in the pavement's lifeLate in the pavement's life 7 - 10 years of service7 - 10 years of service

Aging - How ?Aging - How ?

Early:Early: To simulate the aging that occurs To simulate the aging that occurs due to construction and initial service, we due to construction and initial service, we are going to employ the Rolling Thin-are going to employ the Rolling Thin-Film Oven Film Oven (RTFO)(RTFO). This is a standard . This is a standard AASHTO test method, T 240.AASHTO test method, T 240. Spec.: 85 minutes, 163°C,Spec.: 85 minutes, 163°C,

400 ml of air per minute, 15 rpm400 ml of air per minute, 15 rpm

?

163°C

controls fan

bottle carriageair jet

RRolling olling TThin hin FFilm ilm OOvenven

RRolling olling TThin hin FFilm ilm OOvenvenSample BottlesSample Bottles

Clean BottleBefore Loading

After Loading Coated BottleAfter Testing

Aging - How ?Aging - How ?

Long term: Long term: To simulate the aging that To simulate the aging that occurs due to oxidation over a occurs due to oxidation over a pavement's life, we are going to subject pavement's life, we are going to subject the RTFO residue to time, temperature, the RTFO residue to time, temperature, and pressure. For this we are going to and pressure. For this we are going to develop a pressure aging vessel, develop a pressure aging vessel, (PAV)(PAV). .

?

Aging - How ?Aging - How ?

Long term, Spec.: Long term, Spec.: AASHTO PP1. AASHTO PP1. According to PP1, our RTFO residue is According to PP1, our RTFO residue is

subjected to:subjected to: Temperature: 90 to 110°CTemperature: 90 to 110°C Time: 20 hoursTime: 20 hours Pressure: 2.1 kPaPressure: 2.1 kPa

?

asphaltasphalt

sample pansample pansample racksample rackpressure vesselpressure vessel

airairpressurepressure

temperaturetemperatureprobeprobe

Pressure Aging VesselPressure Aging Vessel

Asphalt binder’s response to Asphalt binder’s response to loading is a function of. . .loading is a function of. . .

1. age 2. temperature

Pavement Temperature, CPavement Temperature, C

- 20- 20 2020 60 60 135 135

TemperaturesTemperatures

Q.Q. What temperatures do we need to address ? What temperatures do we need to address ?

1. Rutting occurs at. . .1. Rutting occurs at. . . 2. Fatigue Cracking occurs at. . .2. Fatigue Cracking occurs at. . . 3. Low Temperature Cracking occurs at. . .3. Low Temperature Cracking occurs at. . .

?

TemperaturesTemperatures

1. Rutting occurs at high pavement 1. Rutting occurs at high pavement temperatures, Ttemperatures, T(high)(high)

2. Fatigue Cracking occurs at intermediate 2. Fatigue Cracking occurs at intermediate pavement temperatures, Tpavement temperatures, T(inter)(inter), and, and

3. Low Temperature Cracking occurs at low 3. Low Temperature Cracking occurs at low pavement temperatures, Tpavement temperatures, T(low)(low)..

?

Performance Grade Performance Grade IncrementsIncrements

Average 7-day Maximum PavementTemperature

46 52 58 64 70 76 82

Average 1-day Minimum PavementTemperature

-10 -16 -22 -28 -34 -40 -46

Superpave Asphalt Binder Superpave Asphalt Binder SpecificationSpecification

Grading System Based on Grading System Based on ClimateClimate

PG 64-22PG 64-22

PerformancePerformanceGradeGrade

Average 7-dayAverage 7-daymax pavementmax pavement

design tempdesign temp

Min pavementMin pavementdesign tempdesign temp

FatigueFatigueCrackingCrackingRuttingRutting

PAVPAV - aging - aging

RTFORTFO - aging - aging No aging No aging

Pavement AgePavement Age

ConstructionConstruction

[RV][RV][DSR][DSR]

Low TempLow TempCrackingCracking

[BBR][BBR]

[DTT][DTT]

Dynamic Shear Rheometer, Dynamic Shear Rheometer, DSRDSR

Apply a oscillating shear stressApply a oscillating shear stress Measure strainMeasure strain

A materials modulus isA materials modulus is Modulus = Stress / StrainModulus = Stress / Strain A measure of material stiffness A measure of material stiffness

Dynamic Shear Rheometer, Dynamic Shear Rheometer, DSRDSR

AB0 20 40 60 80 100 120

-15

-10

-5

0

5

10

15

A

B

Fixed Plate

AB0 20 40 60 80 100 120

-15

-10

-5

0

5

10

15

A

B

C C

A

Fixed Plate

Dynamic Shear Rheometer, Dynamic Shear Rheometer, DSRDSR

0 20 40 60 80 100 120

-15

-10

-5

0

5

10

15

Stra

in

0 20 40 60 80 100 120-15

-10

-5

0

5

10

15

App

lied

Stre

ss

= 20

= 20

Elastic Response

= 0°

Ap

plie

d S

tres

sS

trai

n

0 20 40 60 80 100 120

-15

-10

-5

0

5

10

15

Stra

in

0 20 40 60 80 100 120-15

-10

-5

0

5

10

15

App

lied

Stre

ss

Viscous Response = 90°

= 20

= 20

Ap

plie

d S

tres

sS

trai

n

0 20 40 60 80 100 120-15

-10

-5

0

5

10

15

Stra

in

0 20 40 60 80 100 120-15

-10

-5

0

5

10

15

App

lied

Stre

ss

Visco - Elastic = 30°

Ap

plie

d S

tres

sS

trai

n

DSR provides GDSR provides G** and and

GG**, Complex Shear Modulus, Complex Shear Modulus , Phase Angle, Phase Angle

GG** / sin / sin Correlates to rutting resistance.Correlates to rutting resistance.

GG** sin sin Correlates to fatigue resistance.Correlates to fatigue resistance.

Rutting Specification - Rutting Specification - Minimum Stiffness @ TMinimum Stiffness @ T(high) (high)

GG** / sin / sin > 1.00 kPa > 1.00 kPa on unaged binderon unaged binder

GG** / sin / sin > 2.20 kPa > 2.20 kPa on RTFO aged on RTFO aged binderbinder

FatigueFatigueCrackingCrackingRuttingRutting

PAVPAV - aging - aging

RTFORTFO - aging - aging No aging No aging

Pavement AgePavement Age

ConstructionConstruction

[RV][RV][DSR][DSR]

Low TempLow TempCrackingCracking

[BBR][BBR]

[DTT][DTT]

Fatigue Cracking Specification Fatigue Cracking Specification - Maximum Stiffness @ T- Maximum Stiffness @ T(inter)(inter)

GG** sin sin < 5000 kPa on < 5000 kPa on PAV aged binderPAV aged binder

FatigueFatigueCrackingCrackingRuttingRutting

PAVPAV - aging - aging

RTFORTFO - aging - aging No aging No aging

Pavement AgePavement Age

ConstructionConstruction

[RV][RV][DSR][DSR]

Low TempLow TempCrackingCracking

[BBR][BBR]

[DTT][DTT]

Superpave Binder SpecificationSuperpave Binder Specification Low Temperature CharacterizationLow Temperature Characterization

The Bending Beam Rheometer (BBR) The Bending Beam Rheometer (BBR) determines the Creep Stiffness (S) of an determines the Creep Stiffness (S) of an asphalt binder at low temperatures. asphalt binder at low temperatures.

If a binder is too stiff at service temperatures, If a binder is too stiff at service temperatures, you can expect low temperature cracking.you can expect low temperature cracking.

BBending ending BBeam eam RRheometer, heometer, BBRBBR

FluidBath

Deflection Transducer

Load Cell

Asphalt Beam

Air Bearing

LoadingFrameSupports

Control andData Acquisition

Thermometer

BBending ending BBeam eam RRheometer, heometer, BBRBBR

acetatestrips

rubber O-ringsaluminum mold

binder specimen in mold

125 mm

6.35 mm

12.7 mm

BBending ending BBeam eam RRheometer, heometer, BBRBBR

980 mN (100 g) Load

Asphalt BeamDeflected PositionAsphalt Beam

Original Position

BBending ending BBeam eam RRheometer, heometer, BBRBBR

TimeTime

Test LoadTest Load

DeflectionDeflection

TimeTime

BBending ending BBeam eam RRheometer, heometer, BBRBBR

60 sec Time

Deflection

(t)

simulates stiffness after2 hours at 10 °C lower temp

BBR Data - RelaxationBBR Data - Relaxation

Log CreepStiffness, S

Log Loading Time

slope = m-value

60 sec8 15 30 120 240

PG Spec

Low Temperature Cracking Low Temperature Cracking SpecificationSpecification

Maximum Creep Maximum Creep Stiffness Value (S)Stiffness Value (S) S < 300 MPaS < 300 MPa

Minimum m-valueMinimum m-value m > 0.300m > 0.300

Other PG Binder Tests . . .Other PG Binder Tests . . .

Q.Q. What about Construct-ability ? What about Construct-ability ?

A.A. A better word might be Pump-ability. A A better word might be Pump-ability. A concern raised during SHRP was the need concern raised during SHRP was the need to address modified systems. Heavily to address modified systems. Heavily modified systems can literally burn-out modified systems can literally burn-out pumps. To address this, we will use ASTM pumps. To address this, we will use ASTM D 4404, "Brookfield Rotational D 4404, "Brookfield Rotational Viscometer."Viscometer."

FatigueFatigueCrackingCrackingRuttingRutting

PAV PAV - aging - aging

RTFORTFO - aging - aging No aging No aging

Pavement AgePavement Age

ConstructionConstruction

[RV][RV][DSR][DSR]

Low TempLow TempCrackingCracking

[BBR][BBR]

[DTT][DTT]

Rotational ViscometerRotational Viscometer

sample chamber

spindle

asphalt sample

applied torquefrom motor

Rotational ViscometerRotational Viscometer

digitalreadout

temperaturecontrollerthermo -

container

(ThermoselTM)

spindle extension

Brookfieldviscometer

controlkeys

Rotational ViscometerRotational Viscometer

Rotational Viscometer Rotational Viscometer SpecificationSpecification

Viscosity @ 135ºC < 3.0 Pa-sViscosity @ 135ºC < 3.0 Pa-s

Run viscosity at both 135ºC Run viscosity at both 135ºC and 165ºC to determine and 165ºC to determine laboratory mixing and laboratory mixing and compaction temperaturescompaction temperatures

.1

.2

.3

.5

1

10

5

100 110 120 130 140 150 160 170 180 190 200

Temperature, CTemperature, C

Viscosity, Pa sViscosity, Pa s

Compaction RangeCompaction Range

Mixing RangeMixing Range

Lab Mixing & Compaction TemperaturesLab Mixing & Compaction Temperatures

Asphalt binder’s response to Asphalt binder’s response to loading is a function of. . .loading is a function of. . .

1. age 2. temperature 3. rate of loading

60 C60 C

25 C25 C

1 hour1 hour

1 hour1 hour

Time vs. TemperatureTime vs. Temperature

10 hours10 hours

Effect of Traffic Speed on Effect of Traffic Speed on Binder StiffnessBinder Stiffness

0

2

4

6

8

10

RTFO

DSR

, kPa

52 58 64

Test Temperature, ºC

PG 64-22

50 mph (10 rad/ s) 20 mph (4 rad/ s) 5 mph (1 rad/ s)

PG Spec2.2 kPa

FHWA ALF Binder StudyFHWA ALF Binder Study

0

5

10

15

20

25

30

PG 58-28 PG 64-22 PG 76-22

AC-10AC-20PMA

Rut Depth, mmRut Depth, mm

30 mm30 mm

Asphalt Binder GradeAsphalt Binder Grade

24 mm24 mm

4 mm4 mm

Rut Depth @ 5000 passes of ALFRut Depth @ 5000 passes of ALF 11 mph @ 58ºC11 mph @ 58ºC

Effect of Loading Rate on Effect of Loading Rate on Binder SelectionBinder Selection

ExampleExample for 55 mph highwayfor 55 mph highway

PG 64-22PG 64-22 for 30 mph highwayfor 30 mph highway

PG 70-22PG 70-22 for intersectionsfor intersections

PG 76-22PG 76-22

Standard GradeStandard Grade

Slow Slow - Bump- Bump one gradeone grade

Stopped Stopped - Bump - Bumpone gradeone grade

SUPERPAVE Asphalt SUPERPAVE Asphalt Binder SpecificationBinder Specification

Selection is based onSelection is based on ClimateClimate Traffic speedTraffic speed Amount of traffic - Amount of traffic -

measured in ESALsmeasured in ESALs PG gradePG grade Asphalt content of Asphalt content of

mix - durabilitymix - durability

PG 70 - 22 = 70 - - 22 = 92Binder may be modified!!

PG 76 - 22 = 76 - - 22 = 98PG 76 - 22 = 76 - - 22 = 98Binder Binder willwill be modified !! be modified !!

““Rule of 92”Rule of 92”

Is the PG Binder Modified ?

(Depends on Asphalt Source!)

Asphalt ModifiersAsphalt Modifiers

Change effects of temperature on physical propertiesChange effects of temperature on physical properties Reduce effects of aging/oxidation Reduce effects of aging/oxidation Improve adhesion to aggregatesImprove adhesion to aggregates

Vis

co

sit

y

Temperature

“Hard” asphalt

“Soft” asphalt

Comp MixService

Fluid

Semi-solid

Modification ConceptModification Concept

“Ideal” Asphalt

Modifiers that affect consistency:Modifiers that affect consistency:

Natural Asphalts (TLA)Natural Asphalts (TLA) ChemicalsChemicals OxidantsOxidants FibersFibers PolymersPolymers

Asphalt ModifiersAsphalt Modifiers

PolymersPolymers

From Greek: “many parts”From Greek: “many parts” High molecular weight molecules formed from High molecular weight molecules formed from

combining simpler molecules/chemical compoundscombining simpler molecules/chemical compounds Styrene- Butadiene-Styrene (SBS) is most widely used Styrene- Butadiene-Styrene (SBS) is most widely used

polymer in asphaltpolymer in asphalt

SS SSS

B

BB POLY-BUTADIENE

POLY-STYRENE

Rubber band

Disposablefork

What is SBS?

LINEAR SBSS SB

RADIAL SBSS SB

SB

What is SBS?

What is SBS?What is SBS?

Styrene-Butadiene-Styrene-Butadiene-StyreneStyrene

Styrene provides Styrene provides stiffness at high stiffness at high temperaturestemperatures

Butadiene gives Butadiene gives flexibility at low flexibility at low temperaturestemperatures

Complete dispersion of Complete dispersion of SBS in asphalt provides SBS in asphalt provides best performancebest performance

How is PMA Produced?How is PMA Produced?

Start with PG 64-22Start with PG 64-22 Dissolve and Cross-link SBS MoleculesDissolve and Cross-link SBS Molecules

Reaction TimeReaction Time Constant AgitationConstant Agitation Constant HeatConstant Heat

Test Asphalt PropertiesTest Asphalt Properties Performance PropertiesPerformance Properties Homogenous MaterialHomogenous Material ConsistencyConsistency

SBS in Asphalt - Beginning

SBS Intermediate Curing

Finished SBS Modified Asphalt

Superpave Superpave PlusPlus Binder Binder SpecificationsSpecifications

Used to ensure Used to ensure polymer-modificationpolymer-modification ExampleExample:: PG 76-22 PG 76-22 Plus Plus

Maximum phase angle Maximum phase angle of 75 degrees of 75 degrees

Test methodsTest methods DSR Phase Angle DSR Phase Angle

(Engineering value)(Engineering value) Amount of Stretch Amount of Stretch

and/or Recovery and/or Recovery (Empirical)(Empirical)

Elastic RecoveryElastic Recovery

Neat doesn’t recover

Modified recovers

1 2

3 4

PG Binder Selection for AirportsPG Binder Selection for Airports

How do we get from ESALs How do we get from ESALs to Airplanes?to Airplanes?

Airfield Asphalt Pavement Airfield Asphalt Pavement Technology Program Technology Program (AAPTP)(AAPTP) Research funded by AIR-21Research funded by AIR-21 Managed by Auburn Managed by Auburn

UniversityUniversity Primarily will research Primarily will research

adapting Superpave to adapting Superpave to airfieldsairfields

Until research is complete – Until research is complete – common sense guidelines common sense guidelines developed by FAA and DODdeveloped by FAA and DOD

FAA and DoD FAA and DoD GeneralGeneral Guidelines for Guidelines for Binder Grade Selection on AirfieldsBinder Grade Selection on Airfields

Consult with local DOTConsult with local DOT Determine grades that are typically being used and are Determine grades that are typically being used and are

available for the particular area available for the particular area Determine the Determine the “Standard Grade”“Standard Grade”

Typically used for highways with less than 10 million ESALsTypically used for highways with less than 10 million ESALs Sufficient on most GA airports Sufficient on most GA airports

Consider Consider ‘Bumping’‘Bumping’ for top 5 inches for top 5 inches ifif concerned concerned Past performance?Past performance? High tire pressures?High tire pressures? Standing or slow traffic (stacking on TWs)?Standing or slow traffic (stacking on TWs)? Channelized traffic (alleyways)?Channelized traffic (alleyways)?

For Aircraft < 12,500 lbs For Aircraft < 12,500 lbs PG 64-22PG 64-22

For Aircraft < 100,000 lbs For Aircraft < 100,000 lbs PG 70-22 or PG 76-22PG 70-22 or PG 76-22

For Aircraft > 100,000 lbs For Aircraft > 100,000 lbs PG 76-22 or PG 82-22PG 76-22 or PG 82-22

Need to Consider Traffic FlowNeed to Consider Traffic Flow

Grade Bumping Example - Airfields

The higher theGrade, the stiffer

the binder. The more rut

resistance.

PG 82PG 76PG 70PG 64PG 58

Rule # 1

The lower thenumber, the more

resistant tothermal cracking.

PG - 22

- 28

-34

Rule # 2

Rule # 3 PG 82O 22O

PG 76O 22O

PG 70O 22O

PG 64O 28O

PG 64O 22O

PG 58O 28O

104O

98O

92O

92O

86O

86O

The greater the difference The greater the difference the higher the cost.the higher the cost.

Mix Cost + 3 - 5%

Mix Cost + 15-20%

CONCLUSIONSCONCLUSIONS Training needed for everyone if Training needed for everyone if

SUPERPAVE is to be used SUPERPAVE is to be used successfully successfully

PG Grade System provides the PG Grade System provides the right asphalt for varying climate right asphalt for varying climate and traffic conditionsand traffic conditions

SUPERPAVE places more tools in SUPERPAVE places more tools in the Pavement Designers’ Tool Boxthe Pavement Designers’ Tool Box

Designers can solve pavement Designers can solve pavement problems they were unable to in problems they were unable to in the past using SUPERPAVEthe past using SUPERPAVE

SUPERPAVE

Questions?Questions?