Bitumen Rejuvenator Diffusion as Influenced by Ageing

ABSTRACT This paper describes studies to illuminate the process of mixing old and new binder during asphalt recycling, or, more precisely, mixing by diffusion. FTIR-ATR (Fourier Transform Infrared Spectroscopy by Attenuated Total Reflectance) is used to study effects of the degree of ageing on the diffusion process. Generally, diffusion rates are influenced by temperature, size and shape of the diffusing molecules and the viscosity of the media in which the diffusion takes place. Since bitumen ageing normally leads to a considerable increase in viscosity, it was decided to investigate its influence on the diffusion process. The results presented in this study imply that it is the maltene phase viscosity that governs the diffusion rate rather than the viscosity of the bitumen as a whole. As the changes in maltene viscosity due to ageing are found to be small, it is postulated that ageing does not have a significant effect on the diffusion process.