Past and on-going NCDOT research projects have demonstrated substantial variability in the agglomeration, recycled binder availability, and recovered binder properties of reclaimed asphalt pavement (RAP) and recycled asphalt shingle (RAS) materials within North Carolina. These recycled material characteristics are not captured in current quality assurance and control measures. Furthermore, a recent operational review of asphalt plants in North Carolina indicates that unprocessed and processed recycled material stockpiling, crushing operations, and crushing frequency vary.
Illustration of the premise behind using sieve analysis to estimate recycled binder availability.
An in-depth study is needed to identify how recycled material stockpiling and processing practices impact the variability of RAP and RAS properties within stockpiles and among plants. Furthermore, an assessment of how changes in recycled material properties affects asphalt mixture performance is needed to understand the practical implications of variability. Collectively, this research could inform modification of the NCDOT's specifications to improve the consistency of RAP and RAS sources and, in turn, help to achieve reliable mixture performance.
The objectives of the proposed research are to:
(1) identify how recycled material stockpiling and processing practices affect the consistency of RAP and RAS properties within stockpiles and among plants,
(2) evaluate the impacts of recycled material variability on asphalt mixture performance, and
(3) propose modifications to the NCDOT's current specifications to improve the consistency within and across RAP and RAS stockpiles within North Carolina.
The research results will yield improved specifications that may improve the overall performance and consistency of RAP/RAS mixtures in North Carolina.
