Physicochemical and pyrolysis properties of SARA fractions separated from asphalt binder

To further understand thermal properties of asphalt binder, four fractions, namely saturates, aromatics, resins and asphaltenes (SARA), were first separated from asphalt binder. Then, physicochemical and pyrolysis properties of SARA fractions were characterized. The results indicate that the contents of aromatics and resins in asphalt binder are higher than that of saturates and asphaltenes. The number-average molecular weights show a successive increase trend from saturates to asphaltenes. Saturates and aromatics contain similar bonds or functional groups, and aromatics contain a smaller number of saturated hydrocarbons than saturates. Also, resins and asphaltenes show several similar transmittance peaks in Fourier transform infrared spectroscopy (FTIR) spectra. Saturates, aromatics and asphaltenes contain more saturated hydrocarbons than that of resins. Further, FTIR spectra of saturates and aromatics are more similar to that of asphalt binder. Some chemical compositions, bonds and functional groups are only shown in FTIR spectra of SARA fractions through which asphalt components can be further understood. Furthermore, differential thermogravimetry curves of asphalt binder and its SARA fractions exhibit obvious unimodal characteristics, indicating that their pyrolysis processes are one-step reaction. The residue yield ratios, the temperatures corresponding to initial decomposition temperature, the main decomposition range and the maximum mass loss rate successively increase from saturates to asphaltenes. It is concluded that the thermal stability of each SARA fraction is successively increased from saturates to asphaltenes.