Effects of Inert and Active Fillers and Their Physicochemical Properties on Asphalt Mixture Performance

The primary objective of this study is to assess the impact of various inert and active fillers, along with their physicochemical properties, on the laboratory performance of asphalt mixtures. To achieve this objective, various fillers, including active fillers derived from industrial wastes, are sampled, processed, and evaluated. Two state-approved asphalt mixes, a stone matrix asphalt (SMA) and a surface mixture, were selected. For each selected filler, the study characterizes its physical and chemical properties and its influence on the mixture’s laboratory performance against major distresses, specifically, rutting, durability, moisture resistance, and cracking. Results indicate an acceptable correlation between the physical and chemical characteristics of the fillers and the performance of the mixes prepared with these different filler materials. Concerning laboratory-mixed performance, mixes containing industrial fillers, particularly fly ash and steel slag, exhibit better rutting and cracking performance than the control mixes for SMA and surface mixes. In relation to durability, the control mix and steel slag appear to enhance the durability of the surface mixtures. SMA, on the other hand, consistently demonstrates robust performance across filler types. For moisture-damage resistance, the tensile-strength ratio is higher for the different industrial filler materials, especially fly ash and steel slag, than for the control filler. In summary, this study recommends using fly ash and steel slag powder as replacements for mineral fillers in asphalt mixtures. These industrial waste-derived fillers are found to outperform conventional fillers while allowing the reuse of industrial waste in the road infrastructure.