Thermal and structural characterization of bitumen by modulated differential scanning calorimetry

This paper presents the results of investigation of model bitumens, prepared by mixing of individual fractions of bitumen (saturates, aromatics, waxes, resins and asphaltenes) in various ratios, using modulated differential scanning calorimetry and dynamic temperature sweep test. It was shown that, depending on the content of various fractions, bitumen has structural phases of different compositions. When there are no saturated hydrocarbons in bitumen, it has an amorphous structure. Low molecular weight saturated hydrocarbons form a weakly ordered phase in the bitumen at low temperatures (− 42 to − 14 °C), and high molecular weight saturated hydrocarbons—an ordered phase in the middle temperature range (− 10 to 70 °C). Asphaltenes form the amorphous phase at high temperatures (70–90 °C). The presence of these phases in bitumen is recorded on the heat flow curves in the form of glass transition effects, effects of cold crystallization and melting. At a high content of the ordered phase of high molecular weight hydrocarbons and the amorphous phase of asphaltenes, a gel structure is formed in the bitumen.