An investigation of the asphalt blending during recycling using the analytical solutions of the binder diffusion models

Diffusion occurs during the blending process of asphalt recycling. The coefficient of diffusion between any two diffusing materials in asphalt recycling is estimated as a constant value, which is found to vary in the order of 10−9–10−16 m2/s in past studies. In this study, Fick's law of diffusion is solved analytically and modelled to simulate asphalt binder diffusion. A comparative study is performed among the models used to study the variability in asphalt binder diffusion. It is observed that the binder concentration gradients are inconsistent with similar initial and parametric values with the change in the boundary conditions adopted in the binder diffusion models. Similarly, the coefficient of diffusion predicted by the models varies for the models adopted under a constant time. From a comparative study of the models, it is observed that the complete blending condition may not be achieved in some cases.