Perform an investigation of the effects of increased reclaimed asphalt pavement (RAP) levels in dense graded friction courses.
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2015-04-01
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Abstract:In this study, a total of 28 mixture combinations were designed and evaluated to
determine the maximum allowable amount of reclaimed asphalt pavement (RAP)
material in friction courses without jeopardizing pavement cracking performance. The
experimental factors included two RAP sources, four RAP contents, two virgin binders,
and two mixture conditioning levels. RAP binder was recovered and blended with
virgin binders at various RAP binder replacement ratios. All blended binders not only
met the FDOT’s specifications for virgin modified binders, but also had satisfactory
binder fracture energy density (FED) values. Increased RAP content resulted in
stronger (higher tensile strength) but more brittle (lower failure strain and lower FED)
mixtures. However, even after long-term oven aging (LTOA) + cyclic pore pressure
conditioning (CPPC), all RAP mixtures exhibited FED values above 0.75 kJ/m3
and ER
values well above1.0, indicating adequate cracking performance. Higher RAP content
generally resulted in higher ER values. Although the increasing trend was reversed
between 30% and 40% RAP content, the ER at 40% RAP was still well above 1.0 and
greater than the ER for 20% RAP mixtures. It should be noted that all RAP mixtures
evaluated not only met Superpave design criteria, but also dominant aggregate size
range and the interstitial component (DASR-IC) requirements. Satisfactory inclusion of
up to 40% RAP was for well-designed mixtures with good gradation characteristics and
with the use of modified asphalt binders
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