Perpetual Pavement Design John D’Angelo Federal Highway Administration Washington, DC Canadian User Producer Group for Asphalt Saskatoon, Saskatchewan Nov. 16 th 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 Strain High Strain = Short Life Low Strain = Long Life Fatigue Theory

Fatigue Cracking Repeated Bending Leads to Fatigue Cracking

Repeated Bending Leads to Fatigue Cracking

Traditional Fatigue Plot

High Strain = Short Life Low Strain = Unlimited Life Unlimited Fatigue Life Fatigue Life Strain Fatigue Theory for Thick Pavements 70

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 1 HMA E 1 Layer 2 Granular Base E 2 Layer 2 Granular Base E 2 Layer 3 Subgrade Soil E 3 h1h1 h2h2 No bottom boundary, assume soil goes on infinitely. No horizontal boundary, assume layers extend infinitely. Tire has a total load P, spread over a circular area with a radius of a, resulting in a contact pressure of p. Pavement Reactions Deflection (  ) Tensile Strain (  t ) Compressive Strain (  v ) Figure 2. Layered Elastic Model Representation of a Pavement.

Perpetual Pavement Design No Damage Accumulation Log N Log  Threshold Strain 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-287 Surface 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.

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