Surface Mixtures Incorporating Recycled Plastic and High Reclaimed Asphalt Pavement Contents: 2022 and 2023 Field Trials

About the report

Like many other state highway agencies, the Virginia Department of Transportation is extensively working to consider how to best incorporate recycled materials—such as recycled plastic, reclaimed asphalt pavement (RAP) at higher contents with and without the use of recycling agents (RAs), and other materials—into their roads while maintaining or improving durability. The purpose of the study was to determine if recycled plastic-modified (RPM) asphalt mixtures and high RAP (HRAP) mixtures with RAs require deviation from current practice. The first objective of this research was to evaluate whether the design, production, and paving of RPM asphalt mixtures require a change in current practice. The second objective was to ascertain if the production and paving of RPM mixtures result in the generation of hazardous emissions to the environment. The third objective of the study was to assess if higher RAP content mixtures (RAP content > 30%) containing RAs can be designed, produced, and paved to meet relevant performance specifications. Finally, the study evaluated the short-term performance of RPM mixtures and HRAP mixtures containing RAs.

Two control, five RPM, and three HRAP RA mixtures were evaluated during the six field trials. The mixtures included combinations of different RAP contents, five recycled plastic-based additives, and three RA products. Volumetric and gradation analyses were performed on the mixtures. The Cantabro mass loss test, the indirect tensile cracking test, and the Asphalt Pavement Analyzer test were performed on laboratory-produced design specimens and non-reheated and reheated plant-produced, laboratory-compacted specimens. Additional testing, which included the indirect tensile test at high temperature, the indirect rutting test, dynamic modulus, cyclic fatigue, and stress sweep rutting tests, was performed on reheated mixtures. All findings and conclusions are limited to the mixtures evaluated.

Based on the results for the mixtures tested in this study, modification of mixtures with engineered recycled plastics could provide similar or enhanced cracking performance properties and characteristics compared with unmodified control mixtures if designed properly. Long-term cracking performance data remain a critical key element to assess such types of mixtures. Emissions of polycyclic aromatic hydrocarbons, asphalt fumes, and volatile organic compounds generated from one of the evaluated RPM mixtures during paving operations were consistently low and below the reporting limits provided by the laboratory in many cases. Furthermore, mixtures containing 40% RAP contents and RAs can be designed and produced to meet current balanced mix design performance thresholds and current volumetric properties, gradation, and asphalt content requirements. Moreover, all RPM and HRAP sections are in very good condition. Because the sections were placed in 2022 and 2023, field performance data are preliminary.

It is recommended that the Virginia Department of Transportation districts and the Virginia Transportation Research Council continue to monitor the performance of the RPM and HRAP RA sections evaluated in this study. In addition, it is recommended that the Virginia Transportation Research Council work with the Materials Division and districts to consider conducting additional field trials using RPM and HRAP RA mixtures to assess long-term field performance.

_{Disclaimer Statement:The contents of this report reflect the views of the author(s), who is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Virginia Department of Transportation, the Commonwealth Transportation Board, or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. Any inclusion of manufacturer names, trade names, or trademarks is for identification purposes only and is not to be considered an endorsement.}

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