Methodology for estimating the modulus of elasticity of bitumen under different aging conditions by AFM

This paper presents a micro and nano mechanical analysis method to measure the elastic modulus and properties of bitumen. Tests were performed using the AFM in pulsed force mode to determine the adhesion and stiffness of bitumen. In AFM contact mode, a methodology was developed to determine the modulus of elasticity of the bitumen using the nanoindentation technique for small-volume specimens using a Berkovich tip. Two different sources of bitumen were studied with a performance grade of PG 64 S (22) and PG 64 H (25), in its neat, RTFO, and RTFO + PAV aged conditions. The mechanical properties of the bitumen were analysed from the responses of the measured materials. The AFM images and mechanical results reveal that the properties of the bitumen are considerably affected by aging, associated with oxidation and variations in its morphology. Modulus measured by AFM was also compared to traditional G* measurements from a rheometer, and their relationship analysed.