Multi-scale characterization of the effect of wax on intermolecular interactions in asphalt binder

Abstract

This paper investigates the effect of paraffinic wax (commonly found in bio-oils produced from bio-mass) on the properties of asphalt binder as a commonly used additive in warm mix asphalt technologies. A comprehensive series of laboratory experiments combined with computational analysis was performed on an asphalt binder doped with four different percentages (1%, 3%, 5%, and 10%) of paraffin wax. Differential scanning calorimetry was used to study the effect of wax on physical properties of asphalt binder. Furthermore, rheological characteristics and fracture energy of each wax-doped specimen at sub-zero temperatures was measured to study the effect of wax crystallization on asphalt binder properties. To study intermolecular interactions, molecular dynamics simulation was performed on the wax-asphaltene assembly to study molecular conformation and packing of asphaltene molecules in the presence of wax. The results of molecular simulations provided insights into underlying intermolecular interactions that control rheological behavior. This was further reflected in a reduction of self-association of asphaltene molecules; as the wax concentration increased, the average size of asphaltene aggregates reduced. However, the number of clusters of asphaltene increased as wax concentration increased from 1% to 10% in asphaltene matrix. Accordingly, simulations results combined with laboratory characterization contributed to the understanding of the effects of different concentrations of paraffin wax on asphalt rheological properties.