Potential Contribution of Steel Slag Fillers to Asphalt Mastic in Terms of Microwave Heating Efficiency, Electromagnetic Mechanisms and Fatigue Durability

This paper investigates the potential contribution mechanisms of steel slag fillers in asphalt mastic, covering asphalt-filler interaction mechanisms, microwave heating efficiency, electromagnetic absorption mechanisms, and fatigue durability. The physico-chemical microscopic mechanisms of the steel slag filler, the limestone filler and the interactions between the fillers and the styrene-butadiene-styrene (SBS)-modified binders were characterized. The microwave-heating efficiency of steel slag-based asphalt mastic (SBS-SS) and limestone-based asphalt mastic (SBS-LS) was quantified. The dielectric behaviour of the fillers and the corresponding mastic was further characterized to reveal the electromagnetic mechanisms associated with the microwave heating technology. The stiffness evolution and the fatigue durability of SBS-based bitumen under the effectiveness of steel slag and limestone fillers were assessed by the viscoelastic continuum damage theory model and dissipative energy approaches. The steel slag fillers exhibited a greater potential to promote microwave heat efficiency than the natural stone fillers due to higher ferric oxide compositions. SBS-SS mastics have an overall greater dielectric constant and loss factor than those of SBS-LS mastics, resulting in superior electric field energy storage and conversion capabilities. The addition of steel slag fillers magnifies the load sensitivity of the bitumen and weakens the fatigue impedance and fatigue life of asphalt mastic composites.