Evaluation of Chemical Fractions in Paving Grade Bitumen 50/70 and Effects on Rheological Properties

Generally, paving grade bitumen is characterized by mechanical properties at low, medium and high temperatures (breaking point Fraass, penetration and softening point R&B). However, the origin of the raw oil used for bitumen production has a significant effect on the chemical bitumen characteristics usually described by the asphaltene and maltene colloid model concept. Different chemical analysis methods were applied to differentiate the colloidal properties of the binders. In order to evaluate the potential effects on rheology, 14 bitumen 50/70 samples from different proveniences and producers were analyzed on physical, chemical and rheological properties. For the rheological characterization, complex shear modulus tests were conducted in a temperature range of 20 °C to 90 °C at different frequencies. The physical properties were determined by softening point ring and ball. Chemical groups of binders were characterized by thin layer chromatography (TLC/FID) to differentiate in asphaltenes, resins, aromatics and saturates (SARA-analysis) according to colloid model concept. Furthermore asphaltenes were separated into three fractions of different solubility by dissolution/precipitation procedure. This paper presents the differences between rheological, physical and chemical properties of several bitumen samples, which all represent the requirements on 50/70 according to European Standard EN 12591 and which are commonly applied in German asphalt industry. The paper discusses if the specification system based on conventional characteristics is sufficient for European road industry or if still significant differences in rheological and chemical properties are observed.