Characterization of quarry dusts and industrial by-products as potential substitutes for traditional fillers and their impact on water susceptibility of asphalt concrete

Abstract

Mixing, paving, and compaction of hot asphalt mixtures results in the formation of a three-phase system in which aggregates are represented in different fractions including subsieve particles (<0.063 mm), referred to as filler material. Larger particles interlock and form a skeleton, while the bituminous binder bonds individual grains together. Two filler types are commonly used for the production of asphalt mixtures: (i) lime, hydrated lime, or portland cement and (ii) fine particles retained in the separation units of a mixing plant (known as back/back-house filler) or those separated during aggregate production in quarries (quarry dust). We investigated the impact of several quarry dusts or back fillers as well as of selected treated by-products such as blast furnace slag, finely ground waste gypsum boards, or recycled concrete, all potentially applicable as alternative fillers. Different approaches were adopted to characterize these fillers and assess their impact on the adhesion between bitumen and aggregate in the presence of water, stripping resistance, and effect on the stiffness of the asphalt mixture. The results indicate that the effect of blast furnace slag or recycled concrete is superior to some conventional fillers and that mixing quarry dusts with portland cement or talc is beneficial for rendering the originally hydrophilic dusts more hydrophobic.