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TRANSCRIPT
Asphalt Binders Superpave Binder Tests 1
Asphalt Binders
Superpave Performance Graded Specification
Senior/GraduateHMA Course
Asphalt Binders Superpave Binder Tests 2
Superpave Asphalt Binder Specification
The grading system is based on Climate
PG 64 - 22
Performance Grade
Average 7-day max pavement temperature
Min pavement temperature
Asphalt Binders Superpave Binder Tests 3
Pavement Temperatures are Calculated
• Calculated by Superpave software• High temperature
– 20 mm (.8”) below the surface of mixture
• Low temperature– at surface of mixture
Pave temp = f (air temp, depth, latitude)
www.tfhrc.gov/pavement/ltpp/ltppbind.htm
Asphalt Binders Superpave Binder Tests 4
PG Specification Tests
• Rheology– Fundamental properties related to HMA
performance• Test parameters
– Selected to represent in-service & construction temperatures
• Asphalt binder conditioning– Environmental factors
•Short and long term aging
Asphalt Binders Superpave Binder Tests 5
Rheological Tests Selected
• Concentric Cylinders• Dynamic shear rheometer• Bending beam• Direct tension
Asphalt Binders Superpave Binder Tests 6
RV DSR BBR
Construction
Tests Used in PG Specifications
Asphalt Binders Superpave Binder Tests 7
Construction Asphalt Binder Properties
• Concentric cylinder rheometer– Used to insure a minimum
workability (pumpability) at typical mixing temperature
– Maximum viscosity 3kPa at 135oC (275 F)
Construction
[RV]
Asphalt Binders Superpave Binder Tests 8
RV
DSR
BBR
Rutting
Asphalt Binders Superpave Binder Tests 9
Rutting• High in-service temperature
– Desert climates– Summer temperatures
• Sustained loads– Slow moving trucks– Intersections
Viscous Liquid
Asphalt Binders Superpave Binder Tests 10
Rutting
• DSR testing– Minimum stiffness requirement
•Original asphalt binder•Immediately after construction
–Short term aging Rutting
[DSR]
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High In-Service Temperatures
• Permanent deformation (rutting)• Mixture is plastic• Depends on asphalt binder source,
additives, and aggregate properties
Function of warm weather and traffic
Asphalt Binders Superpave Binder Tests 12
Asphalt Binders Superpave Binder Tests 13
Short Term Aging
• Simulates stiffening of asphalt binder during storage, mixing, and hauling
• Function of:– Oxidation hardening
•Asphalt binder reacts with oxygen•Volatilization of specific components
• Simulated using rolling thin film oven
Asphalt Binders Superpave Binder Tests 14
Short Term Aging• Rolling Thin Film Oven Test (RTFOT)
– Simulates aging from hot mixing and construction
Asphalt Binders Superpave Binder Tests 15
Mass Loss is Monitored
• Calculate mass loss after RTFO
Mass loss, % =Original mass - Aged mass
Original mass
x 100
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RuttingSuperpave DSR test requirements:
G*/sin on unaged (original) asphalt binder > 1.00 kPa
G*/sin on RTFO aged asphalt binder > 2.20 kPa
For the early part of the service life
Asphalt Binders Superpave Binder Tests 17
RV
DSR
BBR
Fatigue
Asphalt Binders Superpave Binder Tests 18
Fatigue Cracking
Function of repeated traffic loads over time(in wheel paths)
Asphalt Binders Superpave Binder Tests 19
DSR
• Aged PG asphalt binder– Since long term performance
problem, include:•Short term aging•Long term aging
• Determine DSR parameters using 8 mm plate and intermediate test temperature
FatigueCracking
[DSR]
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Long Term Aging
• Simulates aging of an PG asphalt binder for 7 to 10 years
• Starts with RTFO aged PG asphalt binder– Additional aging with Pressure Aging
Vessel (PAV)•50 gram (1.75 oz)
Asphalt Binders Superpave Binder Tests 21
PAV Components
Bottom of pressure
aging vessel
Rack of individual pans
(50g of asphalt / pan)
Vessel Lid Components
Asphalt Binders Superpave Binder Tests 22
PAV Testing
• After RTFO aging– 50 gram sample/pan aged for 20 hours
in PAV•Pressure of 2,070 kPa (300 psi)•Test temp 90, 100 or 110o C (194,
212,or 230 F)• The parameter addresses the later part of
the fatigue life
Asphalt Binders Superpave Binder Tests 23
Equipment Examples
Asphalt Binders Superpave Binder Tests 24
RV DSRBBR
Thermal Cracking
Asphalt Binders Superpave Binder Tests 25
Low Temperature Behavior
• Low Temperature– Cold climates– Winter
• Rapid Loads– Fast moving trucks
Elastic Solid
E
Hooke’s Law
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Low Temperature
• Thermal cracks– Stress generated by contraction due
to drop in temperature– Crack forms when thermal stresses
exceed ability of material to relieve stress through deformation•Material is brittle
• Depends on source of asphalt and aggregate properties
Asphalt Binders Superpave Binder Tests 27
Thermal Cracking
Asphalt Binders Superpave Binder Tests 28
Low Temperature
• Two rheological tests– Bending beam
•Stiffness– Direct tension
•Strength
Low TempCracking
[BBR]
[DTT][DTT]
Asphalt Binders Superpave Binder Tests 29
Superpave Requirements
• BBR Stiffness Properties– Max stiffness, S, at 60 seconds of 300
MPa– Min rate of change in stiffness
•Min slope, m, of 0.300 MPa/sec• Strength
– Currently being finalized
Asphalt Binders Superpave Binder Tests 30
Summary
FatigueCrackingRutting
RTFOShort Term AgingNo aging
Construction
[RV] [DSR]
Low TempCracking
[BBR]
[DTT][DTT]
PAVLong Term Aging
Asphalt Binders Superpave Binder Tests 31
QUESTIONS ?