Rheological behaviour of bitumen blending with self-healing microcapsule: Effects of physical and chemical interface structures

Abstract

Rejuvenator-containing microcapsules for spontaneously healing microcracks in bitumen have been developed and are already commercially available. Such smart self-healing approaches are promising for use in developing long-life pavements. The aim of this work was to investigate the rheological behavior of bitumen blended with self-healing microcapsules effected by physical and chemical interface structures. Based on a point of colloids, three self-healing microcapsule samples were used, with average diameters of 10, 20, and 30 μm. Bitumen composites with various microcapsule contents (1%, 2%, 3%, 4%, and 5%) were produced. Morphological analysis showed that the microcapsules were spherical and did not agglomerate. Fluorescence microscopy and X-ray transmission computed tomography showed that the microcapsules were homogeneously dispersed in the bitumen and did not rupture or agglomerate. The smaller microcapsules had larger specific surface areas. The size and content of the microcapsules affected the physical parameters of the bitumen, e.g., penetration, softening point, and ductility. Fourier-transform infrared spectroscopy showed that the bitumen was chemically linked with the microcapsules via functional group reactions. A dynamic shear rheometer was used to investigate the rheological behaviors of the bitumen/microcapsule samples. The complex shear modulus and phase angle data showed that the microcapsule content and size greatly affected the rheological behavior of the bitumen. The bitumen viscoelasticity depended strongly on the contact area and chemical bonds. A mechanistic analysis was performed to clarify the rheological behavior changes in terms of physics and chemistry. This result of this preliminary analysis will be helpful in the screening and application of self-healing microcapsule products.