Quantitative analysis of bitumen microstructure by atomic force microscopy under repeated heating

This research assessed the influence of repeated laboratory heating and storage on the consistency and properties of bitumen. The most characteristic microstructural cases were created through simulated ageing, followed by quantitative atomic force microscopic (AFM) analysis of critical morphological features. Micrographs were segmented into phases corresponding to the topographical valleys, hills, and intermediate plateaus typical for the AFM of bitumen. The segmented discrete phases were analysed for size distribution and spatial arrangement, while the intermediate space was analysed for local thickness distribution. The simulated ageing conditions substantially affected the surface microstructure and micromechanical integrity of bitumen. This degraded the initially evenly heterogeneous microstructure by drastically increasing its spatial variability and reducing the replicability of results. The reduced regularity of wrinkle geometry (size, shape, and spatial arrangement) was the most obvious consequence. The remarkably higher variability also significantly reduced replicability between specimens, causing quantitative parameters of individual images to diverge drastically.