Abstract
The purpose of this study was to investigate the effect of aggregate surface adsorbed water on the adhesive capacity and nanostructure of asphalt-aggregate interfaces at the atomic scale. Molecular dynamics (MD) simulation was performed to measure and analyze the molecular interactions of asphalt binder with calcite and silica. Radial distribution function (RDF) and relative concentration (RC) were applied to characterizing the concentrations and distributions of asphalt components on aggregate surfaces. In addition, debonding energy and adhesion energy were employed to calculate the variations of interface adhesion energy of the asphalt-aggregate system under different conditions. The obtained results illustrated that the water molecules adsorbed onto the surface of weakly alkaline aggregates inhibited the concentration and distribution of asphalt components near the aggregate surface, decreased adhesion energy between asphalt and aggregates, and changed asphalt nanostructure. Especially, when external free water intruded into the interface of the asphalt-calcite system, the adsorbed water interacted with free water and seriously declined the water damage resistance of the asphalt mixture with limestone as an aggregate and decreased the durability of the mixtures. The water adsorbed onto the surface of the acid aggregate negatively affected the asphalt-silica interface system and slightly reduced the water damage resistance of the asphalt mixture.
Highlights
Asphalt mixtures, which are widely being used in roadway engineering construction, consist of aggregates, mineral powders, and asphalt binders [1]
Molecular dynamics (MD) simulations were employed to investigate the variations of the concentration of asphalt components and the effects of the adhesion ability between asphalt and the aggregate of asphalt components and the effects of the adhesion ability between asphalt and the aggregate under different conditions due to the presence of adsorbed water on the surface of aggregates in asphalt–aggregate interface systems
The following simulation results and conclusions were drawn: (1) In the asphalt–calcite interface, the water adsorbed on the surface of weakly alkaline aggregates significantly decreased the aggregation concentrations of resin and asphaltene and made the distributions of SARA components near the calcite surface more uniform, which seriously affected adhesion energy between asphalt and calcite
Summary
Asphalt mixtures, which are widely being used in roadway engineering construction, consist of aggregates, mineral powders, and asphalt binders [1]. Adhesive capacity between asphalt and aggregate plays a critical role in the structure of asphalt mixtures and has great impact on the service quality of pavements [2,3,4]. The increase of the interfacial bond at the asphalt-aggregate interface improves the mechanical properties of asphalt mixtures and increases the service life of asphalt pavements. The existence of moisture in the asphalt mixture decreases bond strength between the asphalt and aggregate, resulting in water damage to the asphalt pavement and inducing other pavement damages [7,8,9]. Liu et al [10] investigated the interface-cracking performance of asphalt-aggregate
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