Experimental observation of the vascular self-healing hollow fibers containing rejuvenator states in bitumen

Abstract

Hollow fiber containing rejuvenator is a promising smart material for vascular self-healing bituminous materials of pavement. The objective of this work was to experimentally observe the states of self-healing hollow fibers containing rejuvenator in pure bituminous material. Polyvinylidene fluoride (PVDF) hollow fibers containing oily rejuvenator were spun through single-wet-spinning method. The fixed-length hollow fibers with sealed ends were mixed in bitumen forming composite samples. The inter-surface and outer-surface microstructure of hollow fibers were observed by an environmental scan electron microscopy (ESEM). The micropores in fiber-shells were channels for rejuvenator to pass through. X-ray computed tomography (XCT) results indicated that these fibers distributed in bitumen with an integrality state. Three-dimensional reconstruction XCT (3D-XCT) images exhibited the details both of vertical and horizontal distribution of hollow fibers in bitumen. Thermogravimetic analysis (TGA) and a repeated thermal-cycle testament showed that the hollow fibers survived safely in bitumen. No debonding phenomenon was found between the fibers and bitumen. Oily rejuvenator released out of hollow fibers smoothly through the break point of hollow fiber/bitumen composite samples. The break images of hollow fibers in bitumen were also analyzed through 3D-XCT structures. At the same time, the movement tracks of oily rejuvenator out of hollow fibers were observed by a fluorescence microscopy. The rejuvenator permeated through the micropores on a hollow fiber into aged bitumen. These states mean that the self-healing can be triggered through the break points of hollow fibers as well as the self-rejuvenation when bitumen is aging. The above result is evidence that the hollow fibers containing rejuvenator will be a feasible approach to realize the self-healing and self-rejuvenating process of bitumen.