Performance-Related Design Method for Asphalt Mixes That Contain Reclaimed Asphalt Pavement (RAP)

Currently, most highway agencies allow the use of reclaimed asphalt pavement (RAP) in asphalt mixes. However, the aged binder in RAP can increase the brittleness of the mixture and result in less resistance to cracking, especially when a high percentage of RAP is used in asphalt mixes compared to mixes without RAP. Furthermore, the current mix design method for asphalt mixtures that contain RAP is not performance-related. The inclusion of RAP can change the volumetrics of the asphalt mix, such as its asphalt content and voids in the mineral aggregate, which could affect performance. In addition, the use of blending charts does not necessarily ensure that asphalt mixes containing RAP will perform well. Moreover, the use of blending charts demands the extraction and recovery of RAP binder, which involves using toxic chemicals and is costly and time-consuming. Therefore, a practical and performance-related RAP mix design method is greatly needed to ensure the design of well-performing RAP mixes and facilitate the use of RAP in asphalt mixtures. In this study, ten mixes with different percentages of RAP were tested for the mix design. Laboratory performance evaluations were conducted in terms of volumetrics, rutting, fatigue cracking resistance, and low temperature thermal cracking resistance. A performance-related mix design method that incorporates RAP without the need to extract, recover, and grade RAP binder was developed in this study.