Impact of adding warm asphalt mix additives on recycling milled coatings: performance evaluation

The use of warm mix asphalt (WMA) and reclaimed asphalt pavement (RAP) technologies presents challenges in optimizing binder activation and mechanical performance in asphalt mixtures. This study aimed to evaluate the effects of three WMA additives (sunflower oil, WarmGrip®, and natural zeolite) and different RAP contents (30% and 70%) on the rheological and mechanical properties of recycled asphalt mixtures. The research focused on assessing the degree of RAP binder activation, determining the extent of partial activation, and analyzing the impact on tensile strength, moisture resistance, modulus, fatigue life, and deformation resistance. The methodology included chemical and rheological analysis of RAP and modified binders, as well as mechanical testing of recycled mixtures. Results indicated partial RAP binder activation, with 96.16% activation in mixtures containing 30% RAP and 80.77% in those with 70% RAP. Sunflower oil acted as a rejuvenator, reducing binder stiffness and decreasing the maximum PG temperature by 6 °C. The use of natural zeolite improved moisture resistance, resulting in TSR values 20% higher than those of conventional hot mixtures with the same RAP content (70%). Warm recycled mixtures demonstrated enhanced fatigue life and moisture resistance, particularly with WarmGrip®. Overall, the incorporation of WMA additives allowed for enhanced fatigue life and deformation resistance in recycled mixtures, enabling the use of up to 70% RAP without compromising mechanical performance. The findings support the potential of WMA and RAP additives to improve sustainability, cost-effectiveness, and durability in asphalt pavement construction. Graphical Abstract