Self-healing of open cracks in asphalt mastic

Asphalt mastic is a self-healing material. Cracks may develop in the asphalt mixture as a result of different factors, such as repeated traffic loads or freeze–thaw cycles. But, once a crack is open in the pavement, it starts healing and, if it has enough time to complete the process, it can even close completely. Asphalt mastic self-healing properties are directly linked to temperature and to the rest periods it can be classified as a thermally induced self-healing material. Moreover, it is well known that the speed at which this phenomenon occurs is higher with the increase of temperature. In this paper, it is explained that the changes in the self-healing rates with temperature can be related by means of the Arrhenius equation. For that, an apparent activation energy for healing is needed. To calculate it, a series of asphalt mastic beams were broken and healed at different temperatures and the time when the recovery is complete was used to calculate the activation energy. Moreover, capillary flow through the crack was hypothesized as the main cause for healing. Finally, to have a visual prove of this theory, the healing process in one of the asphalt beams was examined through CT-Scan tests.