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Asphalt Concrete Characterization
for Pavement Designs
Ludomir Uzarowski, Ph.D., P.Eng., Golder Associates Ltd., ON
Adjunct Professor, University of Waterloo, ON
CUPGA Edmonton, November 28, 2010
INTRODUCTION
Flexible (asphalt) pavement
design methods
Asphalt concrete testing
Fundamental
Permanent deformation
Fatigue
Low temperature cracking
Moisture damage
Frictional characteristics
Summary
EXISTING PAVEMENT DESIGN METHODS INADEQUATE
Existing pavement design methods
are very limited
Even AASHTO 93 based on road
tests performed in the late 1950’s
Do not effectively deal with high
traffic volumes, new materials and
complex deterioration patterns
MEPDG?
Extensive experience in HMA
characterization available in Canada
Universities
DOT’s and other agencies
Consultants and contractors
PAVEMENT DESIGN REQUIREMENTS
Experience-based Standard sections
Do not require any specific HMA
characterization
Assume HMA mix meets specification
requirements
Empirical AASHTO 93
Layer coefficient
Theory-based (mechanistic
empirical) MEPDG
• Dynamic modulus
• Performance modeling
AASHTO 93 Pavement Design Guide
SN = a1D1 + a2D2m2 + a3D3m3
a1 = 0.4 [log10{EAC/435}] + 0.44
MECHANISTIC - EMPIRICAL
MEPDG
Dynamic modulus
• Measured – Level 1
• Predicted from mix
characteristics – Level 2
• Default – Level 3
Pavement performance
modeling
• Rutting
• Bottom-up fatigue cracking
• Top-down cracking
• Low temperature cracking
ASPHALT LAYERS CHARACTERIZATION
Existing pavement
Field testing
• Falling Weight Deflectometer (FWD)
Cores
Laboratory testing
• Gradation, asphalt cement content
• Strength, volumetrics?
ASPHALT CONCRETE LABORATORY TESTING
Pavement distress mechanisms
Permanent deformation (rutting)
Fatigue cracking
Low temperature cracking
Moisture- induced damage
Frictional characteristics
ASPHALT CONCRETE LABORATORY TESTING
Permanent deformation and
fundamental tests
Fundamental
• Uniaxial and triaxial creep, repeated
loading and strength tests
Empirical
• Marshall test
• Hveem test
Simulative tests
• Asphalt Pavement Analyzer (APA)
• Hamburg Wheel Rut Tester (HWRT)
• French Laboratory Rutting Tester
(FLRT)
ASPHALT CONCRETE LABORATORY TESTING
Fundamental
Uniaxial and triaxial creep and
repeated loading tests
Rutting resistance
Mainly research
ASPHALT CONCRETE LABORATORY TESTING
FundamentalSimple Performance Test (SPT)
• Flow time
• Flow number
Dynamic modulus
Resilient modulus
Evaluates the modulus of the
mix under various temperatures
and traffic loads
-10, 4, 21, 37 and 54°C
25, 10, 5, 1, 0.5 and 0.1 Hz
AASHTO TP 62-07
Higher frequencies = fast
moving traffic
Lower frequencies = slow
moving or static traffic
Modulus is a function of the
stress and strain experienced
DYNAMIC MODULUS TESTING
DYNAMIC MODULUS RESULTS
ASPHALT CONCRETE LABORATORY TESTING
Empirical
Marshall test• Marshall stability
• Flow
Hveem test
SUPERPAVE
Selection of asphalt cement
Performance grade of asphalt cement
Selection of aggregate and gradation
design
Consensus properties
Source properties
Blend design
Mix design
Asphalt cement content
Moisture susceptibility
Performance
No strength or other performance test
SUPERPAVE
SUPERPAVE
SUPERPAVE
SUPERPAVE
ASPHALT CONCRETE LABORATORY TESTING
Simulative tests
Asphalt Pavement
Analyzer (APA)
• Rutting resistance• Fatigue
• Moisture susceptibility
• AASHTO TP 63-09
• Dry of wet test
• Steel wheel on pressurized
rubber hose
• Temperature controlled
chamber
• 8000 cycles
ASPHALT CONCRETE LABORATORY TESTING
Simulative tests
Asphalt Pavement Analyzer (APA)
• Rutting resistance– Typical requirement – not more than 5 mm after
8000 cycles
ASPHALT CONCRETE LABORATORY TESTING
Simulative tests
Hamburg Wheel Rut
Tester (HWRT) Rutting resistance
Moisture susceptibility
Wet test
Steel or rubber wheels
Load 710 N
Temperature controlled chamber
(typical testing temperature 50ºC)
Average wheel speed 1.1 km/h (53
2 wheel passes per minute)
10,000; 15,000; or 20,000 passes
ASPHALT CONCRETE LABORATORY TESTING
Simulative tests
French Laboratory Rut
Tester (FLRT) Rutting resistance
Only dry test
- Testing required by MTQ on medium to high
volume roads
- Pneumatic tire (400 mm diameter, 80 mm wide)
- Tire pressure 600 30 kPa
- Average wheel speed 1Hz
- Load 5000 50 N
- Temperature controlled chamber (typical
testing temperature 60ºC)
- Rutting monitored at 100, 300, 1,000, 3,000 and
10,000 passes
ASPHALT CONCRETE LABORATORY TESTING
Fatigue testing
Fatigue cracking considered mainly
due to underdesigned pavement
structure
PGAC selection
Fatigue HMA mix testing
Diametral test
• Nottingham Asphalt Tester (NAT)
Flexural fatigue beam test
• Interlaken
• MTS
Fatigue testing
Four Point Flexural Bending Beam
Test
ASTM D 7460-08
Cyclical loading applied at a
constant strain (or stress) until
stiffness decreases significantly
Strain 300 to 700 µε
Temperature 21°C
Fatigue life - failure point when
stiffness decreases by 50%
ASPHALT CONCRETE LABORATORY TESTING
Low temperature cracking
PGAC selection
Temperature Stress Restrained Specimen
Test (TSRST)
AASHTO TP10
Samples are hold at a constant length and
cooled at a rate of -10°C/hour
As the temperature drops, samples are
maintained in its original height until failure
The force is monitored and recorded
ASPHALT CONCRETE LABORATORY TESTING
ASPHALT CONCRETE LABORATORY TESTING
Moisture susceptibilityBoiling Water Test (ASTM D3625)
Static Immersion Test (AASHTO T 182)
Lottman Test (NCHRP 246)
Tancliff Test (NCHRP 274)
Modified Lottman (AASHTO T 283)
Superpave
• Tensile Strength Ratio (TSR)
min 80%
Retained stability
• Minimum 70%
ASPHALT CONCRETE LABORATORY TESTING
Frictional characteristicsField testing
• Locked wheel trailer
• Griptester
• British Pendulum Tester
Laboratory testing
• There are not good methods available
• Aggregate polishing characteristics
– Polished Stone Value in the U.K.
• Mixes not oveasphalted
• Coarse texture
• Open-graded friction mixes
SUMMARY
Existing pavement design methods are
very limited
Do not effectively deal with high traffic
volumes, new materials and complex
deterioration patterns
There are number of good HMA
characterization tests available
Extensive experience with these tests by
some agencies and companies in Canada
Use them when required
High volume roads, bus and high truck traffic
routes
New technologies and materials
