Microfluidic synthesis of polymeric fibers containing rejuvenating agent for asphalt self-healing

Micro-cracks are generated inside asphalt materials as a result of the action of external environmental factors, such are aging, extreme temperature and moisture. Asphalt binder is a self-healing material with the ability of automatically repair its damage during rest periods. However, this autonomous process in the damaged asphalts is limited and inefficient at low temperatures. In this sense, several studies for synthesizing encapsulated rejuvenators have been developed in recent years to improve the self-healing capability of bituminous materials and thereby to extend their service life. This paper presents the synthesis of two different Ca-alginate polymeric fibers encapsulating rejuvenator by microfluidic device: i) hollow Ca-alginate polymeric fibers encapsulating rejuvenator jets, and ii) compartmented Ca-alginate polymeric fibers encapsulating rejuvenator droplets. The synthesis mechanism of the fibers was analyzed by hydromechanics, and the effect of different structures on the properties of polymeric fibers was investigated. Also, the improved self-healing properties of asphalt bitumen containing the fibers were studied. Scanning electronic microscopy (SEM), polarizing microscopy (PM), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA) were used to evaluate the fiber synthesis process. The self-healing capability of bitumen with fibers was monitored from a micro-perspective by fluorescence microscopy (FM). It was found that the improved asphalt self-healing process using polymeric fibers containing rejuvenator can be explained in several physical-chemical stages. Tensile stress-recovery tests and modified ductility tests were conducted and demonstrated that the addition of polymeric fibers can enhance the asphalt self-healing property at low temperatures. However, it was proved that the hollow Ca-alginate polymeric fibers play a more significant role in improving the bitumen self-healing ability than compartmented Ca-alginate polymeric fibers due to the higher content of encapsulated rejuvenator inside them.