Microcapsules for self-healing of asphalt mixture without compromising mechanical performance

In this research calcium-alginate capsules containing vegetable oil that can release their content due to a mechanical trigger have been made and mixed in asphalt mixture to improve its natural self-healing properties. The physical, mechanical and self-healing properties of asphalt mixture containing these capsules have been evaluated for the first time. Three different capsule contents were used, with oil-to-bitumen ratio 1.1, 2.8 and 5.5, respectively. Capsules were strongly bonded to the asphalt mixture and results showed similar mechanical performance to that of asphalt with and without capsules in the water sensitivity, particle loss and permanent deformation tests. This shows that capsules for asphalt self-healing can be safely used in the road, without affecting its quality. Asphalt containing capsules had slightly lower stiffness, which can be easily solved by reducing the size of the capsules in the future. Furthermore, a new method for testing asphalt containing capsules was designed and tested. It was found that cracked asphalt mixture with capsules recovered 52.9% of initial strength at 20 °C versus 14.0% of asphalt mixture without capsules.