Modeling of Viscosity and Chemical Structure of Virgin and Aged Asphalt from Different Origins

Abstract

Abstract Viscosity is a crucial rheological indicator of the flow behavior of asphalt binder that affects mixing process, pipeline transportation, and pavement compaction quality. Modeling the viscosity and chemical characteristics of asphalt has been a topic of interest. Herein, three asphalt binders of the same pen grade from different origins named Asphalt A, Asphalt B, and Asphalt C that differed significantly in viscosity were used. A solvent extraction separation experiment was applied to get a sufficient amount of virgin asphalt narrow fractions. A pressure aging vessel (PAV) test was conducted to collect aged asphalts with different aging degrees. Rotary viscosity measurements under different temperatures were conducted, and visco-flow activation energy (Ea) was calculated in accordance with the Arrhenius equation. Their chemical properties were analyzed by saturates, aromatics, resins, and asphaltenes fractions analysis, elemental analysis, gel permeation chromatography, Fourier transform infrared spectrometry, and proton nuclear magnetic resonance (1H-NMR). The essential and quantifiable microstructure parameters affecting asphalt viscosity, including weight average molecular weight (Mw), which determines the dispersion interactions between asphalt molecules, carbonyl index (IC=O) and sulfoxide index (IS=O) represented as polar interactions, aromaticity index (fA) represented as pi–pi interactions, branching index, and average chain length (L), which reflect internal friction when asphalt molecules move, were found and multiple linear combination models were established to describe the relationship between Ea and chemical structure. Compared with the single parameter prediction model in the past, multiple linear combination models have a better prediction effect for asphalt with diverse molecular structures (R2 = 0.9692 for virgin asphalt and R2 = 0.9162 for aged asphalts). In addition, the increased amount in Mw, fA, IC=O, and IS=O after PAV aging led to corresponding viscosity increases especially for Asphalt A with high sulfur content.