Chemo-mechanics of ageing on bituminous materials

Abstract

Ageing of bitumen is a complex process. It is accompanied by major chemical and mechanical changes. In this study, Fourier Transform Infrared (FTIR) spectrometer and Dynamic Shear Rheometer (DSR) tests were utilized to investigate the effect of ageing on the chemical and mechanical properties of bituminous materials. 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 materials. The FTIR tests results were used to quantify the changes in the chemical functional groups and to calculate ageing indices (carbonyl index and sulfoxide index) of bitumen. In addition, the DSR tests results were analysed to determine the evolution of the rheological properties of bitumen. A linear relationship was made between the ageing indices and complex shear modulus, providing thus a chemo-mechanics framework to describe bitumen ageing. The results were validated by using data of field aged samples. Finally, the influence of ageing on the parameters of two viscoelastic models was determined