United States Department of Transportation
i
Developing Recommendations for Allowable RAP Contents in Idaho Asphalt Mixes
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2021-05-01
[PDF-3.43 MB]
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Edition:Final Report 5/18/17-/5/31/21
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Abstract:This research study focused on evaluating the effects of high recycled Asphalt Pavement (RAP) contents on asphalt mix performance. Until recently, the Idaho Transportation Department (ITD) did not impose any restriction on the amount of RAP allowed in an asphalt mix. As a result, pavement sections were constructed in Idaho with up to 54 percent RAP (by binder replacement). Some industry and DOT staff raised concerns regarding this practice. Subsequently, ITD placed a temporary limit of 30 percent as the maximum allowable RAP content in a mix. However, to find a permanent answer to this question, the current research study was initiated in collaboration with Boise State University, and later with Oklahoma State University. Extensive review of published literature was carried out on the effects of high RAP contents on asphalt mixture performance. A survey of state DOTs was carried out to gather information regarding their current practices with respect to maximum allowable RAP contents. Extensive laboratory testing was performed to assess the cracking resistance of different asphalt mixtures collected from across Idaho with varying RAP contents. Recommendations have been provided to help ITD adopt a systematic approach to facilitate the design of and construction with asphalt mixtures with high RAP contents.
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