Diffusion of the rejuvenators into bitumen studied by FTIR-ATR as a function of temperature and bitumen properties

Abstract

The ageing of bitumen reduces the ductility of pavement and results in material hardness. Generally, recycling of asphalt is carried out to reduce the negative impact of ageing. In a conventional hot-mix asphalt recycling process, the bitumen from asphalt pavement is blended with the aggregates and rejuvenating agent.

During the recycling process, all materials are mixed at particular temperature for a short period of time. To achieve high quality recycled asphalt mix, proper blending of aged bitumen with added rejuvenator is necessary for effective performance. The role of rejuvenator to reduce the stiffness of aged bitumen is essentially governed by the diffusion of its molecules into the bitumen. Diffusion is a slow occurring process and largely depends on temperature and intermolecular interactions of diffusing molecules

The primary objective of this thesis was to examine the factors limiting the maximum degree of rejuvenation within the realistic time frame, similar to that observed in field. Temperature, viscosity and softening properties of materials were analyzed specifically to deduce their influence on the diffusion of rejuvenating molecules.

Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) was applied to monitor the diffusion of rejuvenator in two different grades of bitumen. The degree of rejuvenation was found to increase with temperature. However, below the softening point of the bitumen, rejuvenation was not visibly proceeding. The rejuvenation level was also found to increase with decreasing viscosity of the rejuvenating agent.