Atomic force microscopy (AFM) based microstructural and micromechanical analysis of bitumen during ageing and rejuvenation

Aging deteriorates the performance of bitumen whereas rejuvenation can partially restore these properties. Although the macroscale properties of bitumen ageing and rejuvenation have been well documented, the microscale mechanisms are still not well understood. Understanding the microscale properties is deemed critical to fully comprehend the mechanisms of ageing and rejuvenation. This study investigated the topographical, micromechanical, and micro-adhesion properties and their correlations of bitumen in terms of ageing and rejuvenation using an atomic force microscope (AFM). Two types of bitumen were aged to five different levels. Subsequently, one bitumen was rejuvenated using two rejuvenators, applied at five dosages. The 2D and 3D microscale properties of aged and rejuvenated bitumen were then comprehensively characterised. The results suggested that ageing altered the microstructures of bitumen while rejuvenation processes cannot recover these microstructures. Ageing initially increased the roughness and adhesion properties of bitumen, but these properties were seen to be later decreased. The modulus increased with ageing and decreased with rejuvenation. The correlation between adhesion force and rejuvenator dosage was material dependent while the microstructures and micromechanical properties of aged and rejuvenated bitumen were correlated.