Abstract
Balanced Mix Design (BMD) approach aims to set maximum and minimum limits of asphalt binder contents to meet rutting criterion and cracking criterion of an asphalt mixture. This study aims at evaluating the influence of reclaimed asphalt pavement (RAP) source, content, and characteristics on the BMD. There have been a lot of research about using RAP with asphalt mixtures, and studies showed that RAP mixes can have better or similar performance as the virgin mixtures. Therefore, in this paper, two RAP sources from local sources in MA were used to investigate the impact of RAP source and content on the performance of a BMD mixture in terms of rutting and fatigue cracking. Performance testing was done using the Hamburg Wheel Tracking test for rutting, the Illinois Flexibility Index for fatigue cracking at intermediate temperature and Disk-shaped Compact Test for thermal cracking at low temperatures. A BMD approach that relies on performance only of asphalt mixtures was used in this study to design a mixture with 15% RAP content. The performance of the mixture in terms of rutting, fatigue cracking, and thermal cracking were used to determine the optimum binder content by constructing a diagram that has a pass/fail criterion of the three performances. The design binder content for the 15% RAP was used as a start point to design and evaluate the performance of higher RAP contents mixtures. For the higher than 15% RAP content mixtures, the optimum binder content had to be increased for the mixtures to stay balanced. However, increasing binder content is not always the best solution due to the impact of RAP source on the performance because the stiffness of the two sources is totally different. One of the sources had very high stiffness (Brox) which was not able to improve the performance of BMD regardless of the binder content. Increasing binder content might not be efficient due to high costs. Therefore, an economic analysis is a necessity to investigate the efficiency of BMD approach. Moreover, economic analysis was able to provide the best and most efficient options for different traffic volumes.