Pavement Design and Materials Selection -

Surfacing

2011 Transportation Course Joe Leidy, PE Construction Division October 11, 2011

Current Design Procedures

FPS is largely empirical, based on AASHTO design philosophy developed in the 60’s and 70’s

Design procedure estimates required layer thicknesses to support change in serviceability for a predicted cumulative loading.

Supplemented by post-design checks.

FPS Modeling Limitations

Layer thicknesses may not be constructible

Material characterization, environmental effects limited

Post Design Checks: Material characterization still limited

Nature of traffic flow not adequately characterized

ME Design

Better characterization of materials & environmental impact

Various models developed to • tie material properties to behavior under

loading and local environment • tie behavior to accumulation of distress

or loss of ride

Better traffic characterization

Will ME Design Connect the Dots?

Can build a catalog of typical materials/family of materials, but can’t accurately forecast what materials will actually be used.

May have to re-run design once materials are known to evaluate performance Δ or readjust original design

Performance models will still have to be calibrated against field data.

Will ME Design Connect the Dots?

Tools to Bridge the Gap

District experience/SOP

Material Selection Guides for Hot Mix Asphalt and Seal Coats

“Balanced Mix Design” & TxACOL

Selection Guide

TxACOL

Double Click

Most commonly used overlay mix types in Texas are included

Level 3 Input Level 1 Input

AC Material Properties Input

You can import or export dynamic modulus here

When Should Dots be Connected?

Pavement Design Concept Conference

Pavement Design Review/PSE Review

Once Project is Let

Post Completion Deflection Test