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