Clustering mechanisms of calcium species in bituminous medium: an insight to physical effects of hydrated lime filler via molecular dynamics

Abstract

This research work addresses the behavior of a hydrated lime-filled bituminous medium rich in carboxylic acids, specifically dodecanoic acid, to investigate mechanisms underlying known beneficial effects of improvement in performance and durability. Classical molecular modeling is implemented as the theoretical basis. This includes the use of molecular dynamics simulations and mean squared displacement (MSD) dynamic analysis to characterize the molecular mobility of the bituminous moieties. Significant improvement mechanisms occur due to the presence of calcium ions from hydrated lime. These include the agglomeration and formation of large clusters of calcium carboxylate complexes as well as the overall reduction of the mobility of the bituminous system. The self-diffusion coefficient determined from the MSD dynamic analysis is presented as numerical evidence of these, which decreases by two orders of magnitude when comparing the unreacted carboxylic acid-rich system to the reacted hydrated lime-filled system.