<p>This paper evaluates the effect of adding Blast Furnace Dust (BFD), a by-product of the steel industry, on the multifunctional performance of porous asphalt mixtures designed for self-healing permeable pavements. Porous mixtures were prepared with six different BFD percentages (i.e., 0%, 2%, 4%, 6%, 8%, 10% by weight), as substitutes for fine aggregate. The physical, mechanical, hydraulic, electrical, thermal, and self-healing properties of the porous asphalt mixtures were subsequently evaluated. The effect of the chemical, mineralogical, and physical properties of both the aggregate and BFD on microwave heating and healing efficiency was also examined. The healing capability of the mixtures was quantified by measuring the three-point bending strength of specimens before and after microwave-induced healing. X-ray micro-computed tomography (micro-CT) was also employed on core samples to assess the distribution of BFD and the internal porosity. Results showed that the lower density of BFD reduced air void content when used as a fine aggregate replacement. At 4% BFD, hydraulic permeability approached that of the reference mixture, due to its good void distribution and connectivity, as evidenced by µCT reconstruction analysis. Electrical resistivity and thermal conductivity were unaffected by BFD incorporation. Mechanical properties and durability improved under both dry and wet conditions, while energy efficiency during microwave exposure also increased. The highest heating rates were observed in BFD and fine aggregate components. Healing indices generally decreased from the third cycle onward; however, the 4% BFD mixture maintained a high healing index for an additional cycle without adverse effects. In short, incorporating BFD into porous asphalt mixtures improves mechanical performance, durability, and microwave heating efficiency, while supporting multifunctional pavement design and promoting sustainability.</p>