This project investigated how neutron imaging can be used to understand the mechanisms behind the self-healing behavior of asphaltic materials, specifically bitumen and bitumen mastics. Bitumen acts as a binder in asphalt mixtures and has the ability to repair small cracks under suitable conditions, but the microscopic processes driving this self-healing have remained unclear.
The study first established the optimal sample dimensions for neutron transmission, balancing between sufficient penetration and structural detail. Time-series neutron tomography was then employed to monitor the healing of fractured samples with varying hydrated lime filler content, crack volume, and contact area. A 3D image analysis pipeline involving denoising, segmentation, and volumetric quantification was developed to evaluate healing kinetics.
The results demonstrated that initial crack geometry strongly influences the healing rate and that bitumen and mastics containing up to 30% filler exhibited similar healing behavior for small cracks. However, healing efficiency decreased exponentially with higher filler concentrations. The findings established neutron imaging as a powerful tool for non-destructive, time-resolved characterization of asphaltic materials, supporting the development of more durable, self-repairing pavements.