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On the quantification of healing in asphalt materials

Time: Fri 2021-06-11 09.00

Location: Videolänk:, Du som saknar dator /datorvana kontakta / Use the e-mail address if you need technical assistance, Stockholm (English)

Subject area: Civil and Architectural Engineering, Structural Engineering and Bridges

Doctoral student: Remya Varma , Bro- och stålbyggnad

Opponent: Dr Lily Poulikakos, EMPA, Switzerland

Supervisor: Professor Nicole Kringos, Bro- och stålbyggnad; Docent Romain Balieu, Bro- och stålbyggnad

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Asphalt materials exhibit self-healing characteristics. In order to evaluate the healing capabilities of these materials, numerous investigations are carried out by researchers. These investigations include various definitions of healing and mechanical test methods to quantify the extent of healing. Irrespective of these extensive studies, there is no unique method to evaluate the healing in asphalt materials. The biasedness to the test conditions and complexity due to the involvement of other phenomena such as stress relaxation and strain recovery make the characterization of healing a challenging process. The work presented in this thesis includes the development of experimental and analytical approaches to contribute to the understanding of healing in asphalt materials. The thesis focuses on both fracture mechanics and damage mechanics-based approaches to evaluate the healing in asphalt materials. In the first case, three-point bending tests are carried out to characterize the healing following the fracture. The experimental protocol is carefully designed to avoid the effect due to low temperature physical hardening of the material during the rest period. Different healing indices appealing to linear elastic fracture mechanics and viscoelastic fracture mechanics are compared. While healing is generally defined based on the recovery of certain parameters following the rest period, the comparison across healing indices shows that the quantitative interpretations of healing are dependent on the post-processing methods. The damage mechanics-based approach discussed in this study includes creep and recovery tests in shear. Here, unlike the first case, the samples are not fractured during the test. The damage is considered to be a part of the viscoplastic deformation and the recovery of viscoplastic deformation is defined as the healing. The method proposed in this study is useful to isolate the viscoelastic effects to quantify the healing of damage.