Comparative evaluation of warm mix asphalt containing high percentages of reclaimed asphalt pavement

• Different warm mix asphalt (WMA) technologies.
• Combining WMA with high percentages of recycled asphalt pavement.
• Plant-produced warm and hot asphalt mixtures with WMA samples produced on site.
• The effect of paving layers.
• Performance evaluation on rutting, moisture susceptibility and fatigue of 15 mixtures.

This paper compared rut resistance, fatigue resistance and moisture susceptibility of plant-produced asphalt mixtures paved in different structural layers, in which the combined effects of warm–mix asphalt (WMA) technologies and high percentages of reclaimed asphalt pavement (RAP) were evaluated through multiple laboratory performance tests. WMA technologies included foaming process and the addition of surfactant based Evotherm additive into asphalt binder. A total of fifteen WMA and control HMA mixtures were evaluated with RAP content ranging from 0% up to 40%. Laboratory performance tests included asphalt pavement analyzer (APA) rutting, Hamburg Wheel-tracking, flow number, tensile strength ratio (TSR), resilient modulus (MR) ratio, dissipated creep strain energy (DCSEf) method from Superpave indirect tension (IDT) tests, 50% stiffness reduction method and plateau value method from beam fatigue tests. The results showed that WMA-high RAP mixtures generally exhibited less rutting and moisture resistance than HMA-high RAP mixtures but better than WMA-low RAP. On the contrary, WMA-high RAP mixtures expressed better fatigue resistance than HMA-high RAP or HMA-low RAP regardless of WMA technology and pavement layer. In summary, rutting might still be a concern for WMA-high RAP mixtures while fatigue concern may not exist, and WMA-high RAP mixtures showed satisfactory moisture resistance with only one exception of foamed base WMA mixture.