Reducing the variability of multi-source reclaimed asphalt pavement materials: A practice in China

The variability of reclaimed asphalt pavement (RAP) materials obtained from different sources is a major concern for the industry when recycling RAP for recycled asphalt mixtures. Many efforts have been made to minimize RAP variability by pre-mixing, crushing, and sieving of the RAP stockpile. In this study, a perspective for reducing RAP variability is proposed by grouping RAP sources with similar material characteristics, which is expected to minimize such variability from the origin. To is end, an asphalt pavement maintenance project located in South China with 16 RAP sources was selected for the study. Furthermore, material characteristics including aggregate gradation, binder softening point, penetration, and dynamic viscosity of recovered asphalt, for RAP obtained from various sources are analyzed by testing on core samples. After the aggregate gradation is presented via Frechet similarity, a K-means cluster analysis is conducted with the involvement of aggregate gradation, asphalt content, and softening point of recovered asphalt. Then, the RAP sources are grouped into three groups with similar material characteristics. The results show that there is a significant difference in RAP material characteristics even for the same pavement, and the procedure developed in this study helps to reduce the RAP variability while increasing the RAP maximum addition amount for producing recycled asphalt mixture. The results may be of interest to construction contractors and road management departments because this study was intentionally conducted for use in practical applications. (C) 2021 Elsevier Ltd. All rights reserved.