The influence of boundary conditions on the healing of bitumen

Damage in pavements is known to reduce over time when the material is left to rest, this phenomenon is identified as healing. It has been shown that healing has a large influence on pavement performance. However, as the healing mechanism is not fully understood, there is currently no accepted method available to assess the healing performance of an asphalt binder. Healing of cracks can be seen as the sum of two processes, cracked surfaces coming into contact (wetting) and strength gain of the contact area (intrinsic healing). This paper aims to increase the understanding of the process of two surfaces coming into contact. Healing of bitumen is assessed using a novel test method, which allows for controlled variation of the stress state during healing. This method consists of bringing two pieces of bitumen together and allowing them to heal under controlled conditions. The extent of healing is then assessed by testing the healed specimens in direct tension. The results, presented in this paper, show that the stress state at assembly and during healing has a significant impact on the extent of healing.