The national highway network is vital to promote social and economic development in the United States; thus, it is essential to guarantee its durability. Better durability of asphalt concrete (AC) pavements would translate into less maintenance and repair, better ridership quality, and reduced environmental impacts. However, in the current design practice for AC materials, little attention is given to study AC performance and its implications for future durability. Additionally, budget and ecological constraints are continually requiring of pavement engineers to include increasing amounts of alternative materials into AC mixes; their impact on future mix performance, however, might not be captured by current testing approaches. Therefore, improving the tools available to assess AC durability is crucial.
This research studied the laboratory performance of a high-quality Stone Matrix Asphalt (SMA), designed by the Danish Road Directorate, and that of a conventional Illinois dense-graded mix, blended with different dosages of rejuvenator to enhance its performance. The effect of short-term aging on the rejuvenated AC blends was also considered in this research. This study focused on assessing the cracking and rutting potential of the studies mixes using the Illinois Flexibility Index Test (I-FIT) and the Hamburg Wheel Track Test (HWTT). Additionally, mix stiffness and moisture damage susceptibility were evaluated using the output data from I-FIT and HWTT, respectively. The tests results were analyzed using the Illinois Balance Mix Design (I-BMD) approach to evaluate the tradeoffs between flexibility and rutting improvements.
This study found that adding rejuvenator to AC does improve its flexibility characteristics; however, the impact becomes less significant with increasing dosage. However, the flexibility index (FI) exhibited by the SMA was the highest amongst the mixes considered in this study. Aging negatively affects FI, but its impact is somewhat limited. Regarding rutting resistance both types of mixes exhibited similar final rut depths; however, at higher dosages of rejuvenator the dense-graded AC mix becomes excessively soft and experiences rapid failure. Rutting resistance was found to be much more sensitive to the effects of both aging and rejuvenation that FI. Analysis of the moisture susceptibility data revealed that the SMA and the un-modified dense-graded AC mixes were less impacted by moisture damage compared to AC mixes with higher dosages of rejuvenator
