Laboratory Performance and Compositional Evaluation of Bio-Based Recycling Agents

Abstract

This study sought to evaluate the chemical composition of bio-based recycling agents (RAs) as indicated by fatty acids content and their impacts on the rheological properties of virgin and recycled asphalt binders. The study consisted of two phases: Phase 1 evaluated five bio-based RAs using gas chromatography/mass spectrometry (GC/MS) and measured binder properties at low temperatures with a bending beam rheometer (BBR). Based on the collected results, two bio-based RAs were selected for evaluation in Phase 2. Phase 2 verified through rheological (BBR and dynamic shear rheometer) and chemical (gel permeation chromatography and Fourier transform infrared spectroscopy) characterization of the effectiveness of the two selected RAs in improving the performance properties of recycled asphalt binders’ blends. Considering that the overall stability of the fatty acids of a recycling agent blended with an asphalt binder is governed by physicochemical factors related to the state of dispersion of the molecular microstructure rather than the inherent reactivity of the molecular components with oxygen, a fatty acid index (i.e., Δfatty acids) was proposed. Based on the results of this research, the Δfatty acids index was found effective in evaluating the oxidation stability of RAs with different chemical compositions and in screening their impacts on the rheological and chemical properties of recycled asphalt binders.