Technical Papers

Examining the Relationship between Bitumen Polar Fractions, Rheological Performance Benchmarks, and Tensile Strength

Abstract

The chemical composition of a bitumen dictates its rheological properties as well as its performance in an asphalt mixture. Any bitumen comprises a wide variety of complex hydrocarbons, and its chemical composition can be characterized by many different parameters. Similarly, the mechanical properties of any given bitumen are typically characterized based on its time-temperature dependent rheological properties at different stress levels. This study characterizes the chemical makeup of a set of bitumens from several different producers based on their polarity and compares these characteristics to mechanical properties associated with the Superpave performance grading (PG) of bitumen and its tensile strength. To do this, a novel fractionation technique was used to separate the bitumens into chemical fractions, while performance testing was performed on the original bitumens. The results were compared using a statistical analysis software to examine relationships between the chemical fractions and physical properties. The results show that high temperature stiffness is strongly dictated by the asphaltene content and that the low temperature stiffness is strongly dictated by the aromatic and resin content. The useful temperature interval showed a good correlation with asphaltenes and resins. Finally, the tensile strength of the bitumens also showed a strong correlation with SARA parameters. Bitumens that deviated from some of these correlations also showed an uncharacteristic response in some other mechanical or elemental property measurements. The relationship between time-dependent characteristics and polar fractions was not strong and requires further understanding.