Molecular dynamics simulation on asphalt-limestone interfaces considering unconstraint surfaces and individual colloid components

Abstract

In molecular dynamics (MD) simulation, interactions of asphalt-limestone interfaces are investigated inaccurately because applying of constraint aggregate surfaces simplify some kinetic energies. Utilizing unconstrained aggregate surfaces provides a novel insight to understand the intermolecular effect of displacement of unconstrained particles. The influence of mineral structures containing Mg2+ other than calcite on adhesion are also ignored. This study builds various unconstraint surfaces and individual colloid components to reasonably evaluate adhesion and interaction by calculating energy, diffusion, and distribution of asphalt-limestone interfaces. Simulations reveal that asphalt-limestone interactions intensify with aging and higher temperatures. Polarity, primarily from sulfoxide (SO) and carbonyl (CO) groups after aging, amplifies adhesion by enhancing electrostatic forces. Individual SARA (saturate, aromatic, resin, asphaltene) components exhibit higher interaction energies with limestone, and differences in interaction energies of SARA on limestone surfaces cause separation in asphalt. Ca2+ and Mg2+ mainly combine with CO32- ions via ionic binding, forming stable surfaces unaffected by asphalt. The mineral composition has a limited impact on asphalt-limestone interfaces, although magnesite displaying the highest attraction to asphalt due to greater electronegativity of Mg2+. Inside asphalt molecules, polar CO and SO groups and planar sharps exhibit strong attraction to aromatic rings, increasing intermolecular energies and cohesion. Self-agglomeration and stacking of asphaltenes, driven by π-π conjunctions in central-aromatic rings and reinforced by aging.