Functional Characteristics of Dense-Graded Asphalt Surface Mixtures

About the report:

As asphalt mix design criteria evolve beyond prescriptive to performance-based specifications, traditional limits may be challenged in the pursuit of material durability.  As designers explore these limits, it is important to understand how basic design criteria ultimately affect the comfort and safety of the public who travels over these mixtures.

This study assessed the short-term functional (surface)characteristics of pavements constructed using dense-graded asphalt surface mixtures designed with the balanced mix design (BMD) methodology as compared to counterpart mixtures designed using the existing design methodology (Superpave).  Another objective of this study was to establish a functional performance baseline for the Virginia Department of Transportation’s (VDOT) BMD trial mixtures constructed in the 2019 through 2021 construction seasons in terms of friction and macrotexture.  This study also sought to define a potential empirical relationship to link mixture volumetric properties to the surface characteristics of asphalt mixtures in terms of macrotexture.  In this effort, 52 different field projects encompassing pairs of BMD and control mixtures with service lives ranging from 0.1 to 2.8 years were surveyed for friction, macrotexture, and pavement roughness. Descriptive statistics and parametric statistical techniques were used to identify systematic trends or differences in the functional characteristics of the pavements. 

The results showed that application of the BMD methodology resulted in slight changes in volumetric properties and gradations of asphalt mixtures, but these changes mostly fell within the production variability limits of conventionally designed mixtures.  The results also showed that BMD mixtures, on average, provided similar or better friction, macrotexture, and smoothness characteristics.  In addition, similar or more uniform texture characteristics were, on average, obtained for the surfaces receiving BMD mixtures, potentially indicating better construction uniformity.  Further, an empirical model incorporating production volumetric and gradation properties was developed to predict macrotexture. 

The study concludes that based on the results from the sites evaluated, use of the BMD methodology yields similar or better functional surface characteristics when compared to those of conventionally designed mixtures.   

The study recommends the continuation of BMD implementation, as the functional characteristics are either preserved or enhanced with the use of the BMD methodology.  Further, the study recommends the assessment of existing and future BMD projects and continued collaboration among VDOT’s Maintenance Division, Materials Division, and Traffic Operations Division on developing a friction and texture management framework.

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