United States Department of Transportation
i
Development of Special Provision for Mix Design of Foamed WMA Containing RAP
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2019-11-30
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[PDF-3.70 MB]
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Edition:Final Report July 2016 – November 2019
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Abstract:Volumetric properties of an HMA mix and a foamed WMA were investigated in this study to examine if there is a need to develop special provisions for designing foamed WMA mixes containing RAP. To this end, foamed WMA mixes were produced in the laboratory using an asphalt foamed and volumetric properties were determined. Performance tests, namely Hamburg wheel tracking test (HWT) to evaluate rutting resistance, semi-circular bend (SCB) test to evaluate fatigue resistance, and tensile strength ratio (TSR) test to evaluate stripping resistance were conducted. For each mix type, the amount of RAP was varied within the range of ODOT’s interest (25% for S3 and 5% for S4 mixes). It was found that the volumetric properties of an HMA mix and a foamed WMA mix designed in the lab were statistically identical. As a result, the current practice of using the HMA mix design procedure for designing a foamed WMA mix for temperatures considered in this project was found to be acceptable. Consequently, no modifications to this design procedure were recommended. Performance-wise, however, foamed WMA was found to exhibit higher cracking resistance and lower rutting resistance compared to HMA. Because of the presence of moisture from partially dried aggregates at lower mixing and compaction temperatures and use of water in the foaming process, WMA exhibited a lower resistance to moisture-induced damage than HMA. A technology transfer workshop was organized to share the outcomes of this study with ODOT, Oklahoma Asphalt Pavement Association (OAPA) and other stakeholders.
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