Laboratory and Field Performance Evaluation of Pavement Sections With High Polymer-Modified Asphalt Overlays

About the report:

In 2014,researchers at the Virginia Transportation Research Council initiated a study to evaluate the effectiveness of using high polymer-modified (HP) binders in surface asphalt concrete (AC) mixtures. The results were promising enough to support a field study investigating the use of HP binders in asphalt mixtures over jointed concrete pavement.  Since 2015, HP AC overlays have been placed at several sections over existing jointed concrete pavement and cracked asphalt pavements in an effort to mitigate reflective cracking.  The purpose of this study was to assess the viability of using HP AC mixtures in Virginia as a reflective crack mitigation technique or when deemed appropriate as a tool for increased crack resistance on higher volume facilities. 

Information on the state of the practice and lessons learned from the use of HP AC mixtures in the United States and Canada are also provided.  In general, HP AC mixtures have been used in a wide range of applications under heavy traffic on interstates and slow-braking loads at intersections.  No major field-related construction issues in terms of mixing temperatures and n-place compaction of HP AC mixtures were reported and standard construction practices and equipment were used.  Good communication between the polymer/binder supplier and the contractor and solid planning prior to the work being conducted were important lessons learned with regard to paving with HP AC mixtures. The performance characteristics of conventional polymer-modified asphalt (PMA) and HP field-produced mixtures were evaluated in the laboratory in terms of durability and resistance to rutting and cracking.  Based on the mixtures tested in this study, HP AC mixtures showed better performance when compared with PMA mixtures regardless of the mixture type (dense-graded surface mixtures and stone matrix asphalt [SMA]).  Moreover, SMA mixtures showed better performance when compared with surface mixtures regardless of the asphalt binder type (PMA and HP). Overall, SMA-HP mixtures showed the most promising performance among all evaluated PMA and HP mixtures.

Distress survey data collected from VDOT’s Pavement Management System of HP field sections were compiled, documented, and compared with that of their control PMA sections.  The HP sections showed the most promising performance 5 years after construction (2015-2020) regardless of the traffic level and the pre-existing pavement conditions. In general, none of the evaluated mixtures (HP or PMA) was able to stop reflective cracking totally.  Moreover, performance evaluations using the network-level pavement management data were conducted to estimate the life expectancy of HP AC overlays.  Overall, PMA and HP AC overlays had an average predicted service life of 6.2 and 8.3 years, respectively, indicating a 34% extension of performance life of the AC overlays with HP modification.

The study recommends continued assessment of the as-constructed properties in future HP projects for the purpose of compiling a materials characterization database.  Further, the performance of all existing and future HP sections should be monitored.  This will help in updating and revising the service life prediction models and the cost-effectiveness of using HP AC mixtures as the existing sections continue to age and more data are available.  Finally, the use of the balanced mix design approach should be investigated to promote further the design of more durable and longer-lasting PMA and HP mixtures in Virginia.

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