Perpetual Pavement

Perpetual Pavements

North Dakota Asphalt Conference
Bismarck, ND
April 6, 2010

Perpetual Pavement
• Not a new concept
–Full-Depth
–Deep Strength
–Mill & Fill

MS-1

Perpetual Pavement Principles

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1.5 - 3” SMA, OGFC or Superpave

4”
Zone
to
Of High
6” Compression

Max Tensile Strain

High Modulus
Rut Resistant Material
(Varies As Needed)
Flexible Fatigue Resistant
Material 3 - 4”

Pavement Foundation

Fatigue and Rutting

HMA

Repeated
Bending

Leads to
Fatigue Cracking

Base
Subgrade

Repeated
Deformation

Leads to
Rutting

Thinner pavements – High Strain
» Minimize Tensile Strain with Pavement Thickness
» Thin Asphalt Pavement = Higher Strain
» Higher Strain = Shorter Fatigue Life

Compressive
Strain

Indefinite
Fatigue
Life

Strain
Fatigue Life
Tensile Strain

Thicker pavements – Low Strain
» Minimize Tensile Strain with Pavement Thickness
» Thicker Asphalt Pavement = Lower Strain
» Strain Below Fatigue Limit = Indefinite Life

Compressive
Strain
Strain

Indefinite
Fatigue
Life

Fatigue Life
Tensile Strain

Mechanistic Performance
Criteria
Under ESAL

Limit Bending to < 65με
(Monismith, Von Quintus, Nunn,
Thompson)

Thick HMA
(> 8”)
Base (as required)
Subgrade

Limit Vertical Compression to < 200με (Monismith, Nunn)

It starts with the Base
› Bottom-up Design and Construction
› Foundation
» Stable Paving Platform
» Minimize Seasonal Variability and Volume
Change in Service

› Fatigue Resistant Lower Asphalt Layer
› Rut Resistant Upper Asphalt Layers

Fatigue Resistant Asphalt Base
» High Effective Asphalt Content Mixes = Greater Strain
Capability
» Modified Binders = Greater Strain Capability

High Asphalt
Content

Strain

Low Asphalt
Content

Fatigue Life

Indefinite Fatigue Life

Rut Resistant Upper Layers
• Aggregate Interlock
» Crushed Particles
» Stone-on-Stone Contact

• Binder
» High Temperature PG
»