Characterization of Asphalt Filler Mastics with Industrial By-Products as Fillers under the Coupled Effect of Aging and Moisture

An asphalt mix comprises asphalt binder and aggregates of different sizes (coarse and fine) and filler. Even with a smaller share, filler plays a crucial role in the performance of asphalt-filler mastics. The study is motivated by the growing need to preserve natural resources and aims to investigate the utilization of four different industrial by-products/wastes (electric arc furnace slag filler, basic oxygen furnace slag filler, tire pyrolysis char filler, and plastic pyrolysis char filler, and one conventional natural stone aggregate filler (NSAF) in asphalt-filler mastics. Four conditioning environments were used to characterize the chemo-rheological properties of the mastics formulated by these five different fillers: unaged, long-term aged, freeze-thaw, and freeze-thaw of long-term aged mastics. To understand the significance of filler attributes in the filler-asphalt mastic performance, a correlation between various filler characteristics (specific surface area, Rigden voids, methylene blue value, and hydrophilic coefficient) and the mastic properties (multiple stress creep and recovery, linear amplitude sweep, binder yield energy test, and Fourier transform infrared spectroscopy) was also attempted. The fatigue life and elastic recovery of the mastics were negatively affected by the combined effects of aging and moisture. The filler characteristics showed a negligible-to-low association with fatigue parameters and a good correlation with rutting performance. The use of these industry co-products/by-products as fillers is supported by the superior rutting and fatigue performance of steel slag and pyrolytic char fillers compared with the traditional NSAF.