Microscopic studies of binder blending on laboratory recycled asphalt mix

ABSTRACT

During blending between the binders in hot mix recycling, two physical processes occur, namely blending due to diffusion and blending due to mechanical agitation. In the present study, an experimental approach is developed to observe these processes directly on the laboratory recycled asphalt mix samples. Atomic Force Microscopy (AFM) and Confocal Laser Scanning Microscopy (CLSM) are used as the probing tools. The binder concentration profile is estimated at different locations around the reclaimed asphalt pavement material (RAPM) aggregate. Diffusion is observed to be predominant in some of these locations, while, in some other locations, mechanical mixing is observed to be predominant. Assuming that pure Fickian diffusion is happening at those diffusion-spots, the coefficient of diffusion is estimated from the concentration profile at those locations. It is envisaged that the proposed approach would provide a microscopic perspective of the extent of blending during the recycling process.

KEYWORDS:

• Recycled asphalt mix
• diffusion
• mechanical mixing
• reclaimed asphalt pavement material (RAPM)
• virgin binder
• AFM
• CLSM

Acknowledgements

The authors acknowledge the help rendered by the Lab Crystals, Lucknow (for the thin film preparation facility), and staff members of various laboratories of IIT Kanpur, namely Ms. Deepali D. Ubale of Centre for Nano sciences (for AFM facility), Ms. Neetu Dey of Advanced Centre for Materials Science (for CLSM facility), Mr. Rahul Kumar of Earth Sciences (for slicing facility) and Prof. Rajesh Srivastava, Department of Civil Engineering, IIT Kanpur (for the useful discussions on diffusion theories).

Disclosure statement

No potential conflict of interest was reported by the author(s).