Application of FTIR-ATR to characterization of bitumen rejuvenator diffusion

Fourier transform infrared spectroscopy by attenuated total reflectance (FTIR-ATR) has been applied to laboratory studies of bitumen rejuvenator diffusion. Previous studies have given more indications rather than a real understanding of the mechanisms involved. FTIR-ATR can be performed in a relatively easy manner to provide diffusion measurements. In this study, parameters such as temperature, binder film thickness, type of bitumen, and, to some extent, chemical properties of the binders have been investigated. The results show a major influence of temperature on the diffusion rate. The study also shows that the diffusion process can be described using Fick's law. The need for a paper on this topic emanates from the lack of knowledge regarding the diffusion process by which new and old binders are mixed during asphalt recycling. If the process is incomplete, the properties of the final recycled asphalt will be influenced negatively. Further research is required to better understand the process of diffusion in bituminous binders. This can be accomplished by testing other combinations of binders, aged and unaged, as well as by studying the diffusion of selected chemical substances (markers) into bitumen.