Mix Design of Polymer-Modified and Fiber-Reinforced Warm-Mix Asphalts with High Amount of Reclaimed Asphalt Pavement: Achieving sustainable and high-performing pavements

The global desire to move toward sustainable transportation systems encouraged road authorities to adopt warm-mix asphalt technologies and to increase the amount of reclaimed asphalt pavement (RAP) in asphalt mixtures. The reduction of mixing and compaction temperatures through the adoption of specific additives has exhibited several downsides, including low resistance to high temperatures (rutting), incomplete drying of the aggregates, moisture damage, and low durability. However, high RAP percentages provided aging of the asphalt binder, variability in the aggregate gradation and asphalt binder content, and some limitations during plant production. The authors conducted a comprehensive laboratory investigation on several warm-asphalt mixes, including those with high RAP percentages, to evaluate volumetric, mechanical, and long-term performance. A new compound of a polymer-modified and fiber-reinforced system was added to provide comparable performance with respect to polymer-modified hot mixes. The laboratory study evaluated the influence of mixing and compaction temperatures, compaction properties, dynamic modulus and master curves, fatigue behavior, and rutting resistance, among other things. Results showed that warm-mix technologies could be adopted together with high RAP percentages and provide consistent performance in durability similar to that attributed to polymer-modified hot mixes. Recycling materials and lowering emissions while providing long-term performance can therefore be considered a tangible objective; however, a correct mix design was demonstrated to be fundamental.