Towards the decarbonization: Integration of recycled crumb rubber Rapid Digestion Process and reclaimed asphalt on asphalt mixtures

The asphalt industry faces major challenges requiring a critical re-evaluation of established practices. Integration of reclaimed asphalt (RA) and recycled crumb rubber (CR) offers a promising route to decarbonization. But can CR be revitalized as a key contributor to achieving the industry's net-zero emissions target by 2050? This study presents the first European evaluation on asphalt mixtures for motorway surface layer using a liquid rubber-polymer bitumen produced with the new Rapid Digestion Process (RDP), which liquefies up to 50 % CR by bitumen mass (solubility ≥ 99 %). A comprehensive four-phase evaluation was conducted: (1) CR dispersion within bitumen and asphalt mixtures and interaction with aggregates; (2) bitumen behavior (including unaged/aged properties, storage stability, handling, and workability) comparing a new PMB 40/100–80 (20 % CR plus polymer) with PMB 45/80–65 and a highly modified PMB 45/80–75; (3) asphalt mixture behavior (volumetric properties, Marshall, stiffness, water sensitivity, resistance to fatigue, permanent deformation, and macrotexture) of three gap-graded AC14 surf PMB 40/100–80 without/with 30 % RA, compared to three AC14 surf without/with 20 % RA; (4) full-scale application on Portugal’s A6 motorway. Results show that RDP produces storage-stable, high-performance bitumen compatible with up to 30 % RA without rejuvenators or adhesion promoters, lowering production temperatures and bitumen content compared to asphalt rubber (wet process). The new bitumen outperformed conventional PMBs in performance, enhancing material circularity, reducing reliance on virgin resources, and contributing to the industry's carbon neutrality goals. • Novel rapid digestion process digests rubber fully, enhancing performance • Improved fatigue, water and deformation resistance with or without RA • First European motorway trial confirm lab results – no process changes needed • Enables 30 % RA use and 18.65 tCO 2 /km/lane savings – outperforms EAPA 2050 targets • High-tech, low-impact bitumen for net-zero, circular road infrastructure