Determination of Input Data for Stone Matrix Asphalt and Polymer Modified Dense-Graded Mixtures for Use in the Mechanistic-Empirical Pavement Design Guide

About the report:

AASHTO’s Mechanistic Empirical Pavement Design Guide (MEPDG)and AASHTOWare Pavement ME Design software (hereinafter “Pavement ME Design”) provide an improved process for conducting pavement analysis and for developing pavement designs based on mechanistic-empirical principles.  The Virginia Department of Transportation(VDOT) officially adopted the MEPDG procedure for new construction (new alignment, lane addition, and total reconstruction) for interstate and primary routes effective January 1, 2018.  Pavement ME Design requires asphalt mixture volumetrics (asphalt content, air voids, and unit weight) and mechanical properties (dynamic modulus) as Level 1 (i.e., the most accurate) inputs.  Currently, VDOT’s dynamic modulus database has limited data on stone matrix asphalt (SMA) and dense-graded polymer modified(designated “SM-E”) mixtures. 

The purpose of this study was to develop input data for SMA and SM-E mixtures for use in Pavement ME Design.  Material properties (dynamic modulus, volumetrics, and in-place density) catalogued from this study will better reflect the rutting characteristics of SM-E mixtures when used in Pavement ME Design.  These coefficients are also comparable to those incorporated in the latest version of Pavement ME Design, i.e., Version 2.6(hereinafter “V2.6 Pavement ME Design”).

The study recommends that VDOT’s Materials Division consider using the rutting calibration coefficients developed for SM-E mixtures in this study when V2.6 Pavement ME Design is considered for adoption.  However, further calibration/validation will still be needed when V2.6 Pavement ME Design is adopted.  Limited field performance data indicated that certain SMA mixtures are susceptible to higher in-service rutting and rutting progression as compared to SM-E mixtures.  The study recommends a detailed study to address the rutting concern for certain SMA mixtures.

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