Microencapsulation of Rubber- and Polymer-Modified Bitumen for Storage and Transportation

Polymer- and waste tire-rubber-modified bitumen enhance asphalt performance by improving stress dissipation, reducing fatigue, and alleviating aging and oxidation. However, the storage and transportation of modified bitumen, which often requires high temperatures to overcome the challenging rheological characteristics of the material, remain challenging because of thermal degradation, phase segregation, and fouling of containers. Here, we develop a microencapsulation strategy to enable safe solid-state storage and transport of modified bitumen. Microencapsulation is achieved through jetting of the modified binders through a single-nozzle system followed by coating within polyanionic lignin multilayers and hydrated lime to form robust shells. Electron microscopy and confocal fluorescence microscopy imaging show continuous shells without discernible macroscopic pores and cavities. The microcapsules show exceptional thermal and mechanical stability and tolerance to high-humidity conditions. Microcapsules with a diameter of 4 mm show a stress-withstanding ability as high as 131 ± 13.5 kN/m2 and can withstand impact velocities ranging up to 35 and 19 m/s for polymer-modified and rubber-modified binder, respectively. The functional properties surpass transportation requirements for bitumen, including free-fall and long-term storage, while enabling direct application at destination sites with a relatively modest increase in viscosity. This work demonstrates a practical solution for improving the logistics and durability of modified bitumen in asphalt applications.