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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?