Compartmented alginate fibres as a healing agent (rejuvenator) delivery system and reinforcement for asphalt pavemnets

When the cracks within the surface layer of the asphalt pavement are still in an early phase, it is possible to prevent further crack propagation and pavement failure by spraying rejuvenator over the surface of the asphalt pavement. Such a process may increase the life span of the asphalt pavement by several years. However, this method only impacts on the top centimetres of the pavement, cracks originating at the bottom of the asphalt layer will not be healed. The inclusion of encapsulated rejuvenators into the asphalt pavement mix presents an opportunity to overcome these problems to heal the entire pavement. The principle behind this approach is that the fracture energy at the tip of the cracks generated in the pavement will break open the capsules, and release the contained rejuvenator. The rejuvenator will then diffuse within the asphalt binder, thereby sealing the cracks and preventing their further propagation. This paper explores the potential use of compartmented sodium alginate fibres as a new method for incorporating rejuvenators into asphalt pavement mixtures. Such an approach potentially offers the following advantages over spherical microcapsules: due to the high aspect ratio of the compartments in the alginate compartmented fibres there is a higher potential that the containers will encounter a fracture enabling the release of higher amounts of healing agent or rejuvenator), alginate is an organic material and poses no environmental/leaching risks, if not opened via fracture contact, alginate fibres will degrade over time, releasing the healing agent rejuvenator and presenting a secondary self-healing trigger mechanism. This work presents the proof of concept of the encapsulation process, embedding of the fibres in asphalt mixtures and the survival rate of fibres in the asphalt mixture. The research findings support the hypothesis that sodium alginate fibres are another step in the development of self-healing asphalt pavement systems.