Numerical study of sorption of asphalt binders on minerals

During the production of asphalt mixes, specific functional groups of asphalt binder interact chemically with certain reactive sites on the surface of minerals forming compounds that enhance the material resistance to environmental effects. The thermodynamics of surface phenomena between various combinations of functional groups of minerals and asphalt binders has been studied for quite a long time but it remains extremely difficult to control the desired material properties in practice. In this study, the chemical thermodynamics that determine the sorption phenomena and subsequently the relative affinity of asphalt binders onto mineral particles were analysed numerically and discussed. A two-step sorption configuration is studied in a multi-physics tool including reaction-driven mass transport of free species (i.e., carboxylic acid diluted in binder) onto a reactive surface (i.e., calcium functionalized mineral). Based on this configuration, the mechanism of asphalt-mineral interaction was determined at different surface temperatures and reactivity characteristics (i.e., activation energy and reaction kinetics of adsorption). The sorption model is applicable for various scenarios of asphalt-mineral interactions, especially for functionalized surfaces, in which the reaction-driven distribution of concentrations of asphalt adsorbates on minerals can provide useful information once the energetic parameters are known.