Variability Investigation of Reclaimed Asphalt Pavement Materials

Abstract

The maximum permissible content of reclaimed asphalt pavement (RAP) is restricted due to its negative effect on the stability of hot mix asphalt with RAP (HMA-RAP) performance. To address this problem, characteristics of materials, including aggregate gradation, aged asphalt content, and aged asphalt properties, were quantified by testing RAP obtained from different sources. Additionally, the changing law and variability of the indexes are also analyzed. In accordance with the quality requirements of hot mixture asphalt stipulated by the Chinese standard, a control model of the maximum RAP content embraced in recycled asphalt mixture for hot central plant recycling is established. Furthermore, the distribution characteristic of asphalt content with respect to particle size is analyzed. Eventually, a fluctuation range model of blended asphalt penetration is established. The results indicate that (1) the variabilities of aggregate gradation, asphalt content, and aged asphalt properties of RAP are nonnegligible; (2) a control model regarding maximum permissible RAP content in HMA-RAP is proposed based on aggregate gradation and asphalt content; (3) the asphalt content and particle size of RAP are exponentially distributed, and the particle size elevates with the decrease of asphalt content; and (4) the fluctuation range of blended asphalt penetration is related to the asphalt content and penetration of aged asphalt, and the fluctuation range extends with the increasing of RAP content. This paper suggests that, to characterize the variability of RAP with its aggregate gradation and asphalt content, for RAP without pretreatment, the maximum permissible RAP content in HMA-RAP is recommended to be controlled under 30%.