Multiscale understanding of interfacial behavior between bitumen and aggregate: From the aggregate mineralogical genome aspect

Abstract

The interfacial behavior between bitumen and aggregate is not well understood so far since it is sensitive to various factors including chemistry of the components, morphology of the interface, and the environmental and loading conditions. Moreover, the mechanisms of action for different factors occur at distinct time and length scales. The multi-factor and multi-scale natures bring great challenge to the interfacial behavior between bitumen and aggregate. This study aims to exploit a deep understanding of the interfacial behavior from the perspective of aggregate mineralogy at the molecular scale and relate this fundamental understanding to affinity between bitumen and aggregate. For this, the affinity between bitumen and six kinds of aggregates were evaluated by the rolling bottle test, and adhesion mechanisms between bitumen and component minerals were investigated through molecular dynamics simulations. The rolling bottle test results show that the diabase has the best moisture damage resistance, followed by the greywacke I, basalt and greywacke II. The two granite aggregates show the worst moisture damage resistance. The molecular dynamics simulation indicates the existence of competitive adsorption between bitumen and water molecules at the mineral surface, and the penetration capacity of bitumen molecule is greatly affected by the mineral property. Aggregates with higher content of nepheline, chlorite, pyroxene and olivine minerals are more likely exhibit better moisture damage resistance while aggregates with higher content of quartz, plagioclase and calcite minerals do the opposite. The findings from this research provide insights into the underlying mechanism of aggregate mineralogy influence on affinity between bitumen and aggregate.