A preliminary experimental investigation on multi-recycled asphalt pavement in Finland

Abstract This preliminary study investigated the effects of the multiple recycling process (up to three recycling cycles) on the performance characteristics of recycled asphalt mixture containing reclaimed asphalt pavement (RAP), both at the binder and mixture levels. This research built on prior studies from Finland and utilized lab experiments to thoroughly examine these effects. Firstly, loose asphalt mixtures were artificially aged to produce RAP aged once, twice, and three times. Subsequently, a series of Stone Matrix Asphalt (SMA) 16 mixtures were prepared using 50% artificially aged RAP, 70/100 binder, and cellulose fiber, experiencing various levels of recycling cycle. The asphalt mixtures were evaluated for moisture susceptibility, cracking resistance in the low temperatures, and resistance to abrasion due to studded tires. Additionally, dynamic rheological behavior and chemical property changes were tested on asphalt binders, both fresh and aged, through three cycles, which were extracted from their respective mixtures. Results indicated that as recycling iterations progressed, the asphalt mixtures showed improved moisture susceptibility and enhanced resistance to abrasion from studded tires. Although one cycle of recycling had a minimal impact on the low-temperature fracture performance of asphalt mixtures, the fracture energy decreased after three cycles. Regarding asphalt binders, the escalation in recycling iterations improved the high-temperature performance but detrimentally affected fatigue properties. These results support multiple recycling of RAP for Nordic cold-climate surface layers, especially where studded-tire abrasion is critical. Recycling beyond two cycles may increase the risk of low-temperature cracking and require mitigation.