Blending and Diffusion of Recycled Asphalt Pavement and New Approach to Recycling Asphalt Shingle

This study proposed a series of methods to investigate the blending and diffusion process of recycled asphalt mixtures using Fourier-transform infrared spectroscopy (FTIR), fluorescence microscopy and molecular dynamic simulation. A new approach to recycling asphalt shingles in which RAS binder was extracted by a mixed solvent with certain polarity and used as common asphalt binder was also developed.A new parameter, mean grey value (MGV), was derived from the fluorescence image and used to differentiate between recycled and virgin binders as well as their blends. The mobilization rate of plant-produced RAP mixtures was calculated on the basis of surface area proportion of aggregates with different size. Three types of asphalt mixtures, including one warm mix with foaming technology, two hot mixes with or without rejuvenator, were used to validate the proposed method.Two asphaltic models with three components including asphaltenes, resin, and oil were built with different components ratio to investigate the diffusion between virgin and aged binders. In an inter-diffusion model of virgin and aged binders, the diffusion coefficients of binders were not only determined by the diffusion ability itself, but also influenced by the properties of the diffusion acceptor.A new method was proposed to utilize fluorescence microscopy to determine the diffusion coefficient of aged RAP binder in recycled mixtures. The diffusion coefficient was determined by fitting the analytical solution to the laboratory concentration measurements. Comparison of the diffusion coefficient by the proposed method and that using the dynamic shear rheometer (DSR) method shows that the diffusion coefficient determined by fluorescence microscopy was of the same magnitude to, but slightly lower than that by DSR method.The RAS binder was extracted by a mixed solvent with certain polarity and used as common asphalt binder. The use of the mixed solvent of heptane and TCE with a certain proportion through the proposed method could prepare asphalt binder with desired properties. Results indicate that soft asphalt could not dissolve RAS binder at 170 ℃. The binder blend of RAS binder and rejuvenator had a potential antiaging problem because an obvious loss of rejuvenator existed during the aging process.