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Perpetual Pavement Design
John D’AngeloFederal Highway Administration
Washington, DC
Canadian User Producer Group for AsphaltSaskatoon, Saskatchewan
Nov. 16th 2008
Appian way in Italy
Experienced based design
Build it thick
Build it with durable materials
It will last
Pavement Design
• In a modern world can we afford to over design?– Limited resources– Limited money– High demand
• How do we design for just the right performance?
Strain Fatigue Life
Stra
in
High Strain = Short Life
Low Strain = Long Life
Fatigue Theory
Fatigue Cracking
RepeatedBending
Leads toFatigue Cracking
RepeatedBending
Leads toFatigue Cracking
Fatigue Cracking
0.00001
0.0001
0.001
0.01
1.0E+02
1.0E+04
1.0E+06
1.0E+08
1.0E+10
1.0E+12
1.0E+14
Load Cycles to 50% Stiffness (Failure)
Stra
in (S
trai
n/1E
6)
?
Traditional Fatigue Plot
High Strain = Short Life
Low Strain = Unlimited Life
UnlimitedFatigue
Life
Fatigue LifeStrain
Stra
in
Fatigue Theory forThick Pavements
70
4000
5000
6000
7000
8000
0.0E+00 5.0E+06 1.0E+07 1.5E+07 2.0E+07 2.5E+07 3.0E+07 3.5E+07 4.0E+07
Number of Load Cycles
Stiff
ness
, Mpa
70 Micro Strain Test
FAILURE MODES
Eventual Distress
Goal of Perpetual Pavement Design
• Design the structure such that there are no deep structural distresses– Bottom up fatigue cracking– Structural rutting
• All distresses can be quickly remedied from surface
• Result in a structure with ‘Perpetual’ or ‘Long Life’
Surface Distresses Only
Non-Structural Rutting
Top Down Cracking
Dynamic Modulus Test
Soil Modulus Testing
Dynamic Cone Penetration
Rod
Reference
Mass
FWD Testing
Traffic
Layer 1HMA
E1
Layer 2Layer 2Granular BaseGranular Base
EE22
Layer 2Layer 2Granular BaseGranular Base
EE22
Layer 3Subgrade Soil
E3
h1
h2
No bottom boundary, assume soil goes on infinitely.
Nohorizontalboundary, assumelayersextendinfinitely.
Tire has a total load P, spread over a circulararea with a radius of a, resulting in a contactpressure of p.
PavementReactions
Deflection ()
Tensile Strain (t)
Compressive Strain (Compressive Strain (vv))
Figure 2. Layered Elastic Model Representation of a Pavement.
Perpetual Pavement Design
No Damage Accumulation
Log N
Log
ThresholdStrain
French concept – High modulus high binder content base.California concept- High strain tolerance polymer asphalt base.New approach- combine both with stiff agg. base to reduce cost.
New Jersey I-287Surface Cracking
Solution: Mill 4” and Overlay with 5”
Perpetual Pavement› Structure Lasts 50+ years.
» Bottom-Up Design and Construction
» Indefinite Fatigue Life
› Renewable Pavement Surface.
» High Rutting Resistance
» Tailored for Specific Application
› Consistent, Smooth and Safe Driving Surface.
› Environmentally Friendly
› Avoids Costly Reconstruction.
References