Variability of Plant-Produced High Recycled Content Asphalt Mixtures Within a State

The incorporation of recycled asphalt material (RAM) into asphalt mixtures is a widely adopted technique in the asphalt paving industry. U.S. state agencies limit the quantity of reclaimed asphalt pavement and recycled asphalt shingles in asphalt mixtures owing, in part, to concerns about variability in performance. The variability of RAM stockpile properties within a state can lead to inconsistencies in the properties and performance of asphalt mixtures. This study aims to characterize the properties of RAM materials within stockpiles over time and across multiple asphalt plants in North Carolina, U.S. It also evaluates the variability in performance of plant-produced high recycled content mixtures in the state and investigates the potential causes for this variability. Asphalt mixtures and their constituent materials were acquired and characterized from four asphalt plants on two different dates. The results show that, while RAM properties were generally consistent within stockpiles over time, significant variations in binder properties and asphalt content were found across different plants within the state. The majority of the mixtures evaluated showed consistent rutting and cracking performance. Variability in cracking performance across plants could be linked to the properties of the recycled and virgin binders. The differences in cracking and rutting performance between the first and second samples acquired from a given plant closely mirrored asphalt content differences.