Ageing effect on chemo-mechanics of bitumen

Ageing has a significant impact on the chemical and mechanical properties of bituminous materials. In this study, Fourier Transform Infrared (FTIR) spectrometer and Dynamic Shear Rheometer (DSR) tests were utilised to investigate the effect of ageing on the chemical and rheological properties of bitumen. Bitumen films with thickness of 2 mm were exposed to laboratory ageing at various conditions. Specifically, different combinations of ageing time, temperature and pressure were applied on the bitumen samples. The FTIR results were used to quantify the changes in the chemical functional groups and to calculate the combined ageing index (summation of carbonyl and sulfoxide indices) of bitumen. In addition, the DSR test results were analysed to determine the evolution of the black diagrams, crossover frequency and crossover modulus with ageing. A linear relationship was found between the combined ageing index and the distance in the crossover map, providing thus a chemo-mechanics framework to describe bitumen ageing. The results were validated by using data of field aged samples.