Functional performance of Fe-doped soft magnetic geopolymers: Influence of S/L ratio and Fe content

Soft magnetic geopolymer composites (SMGCs) are emerging as functional materials for enhancing magnetic field interaction and thermal response in airport pavement induction-heating systems. This study investigates the effects of Fe powder content (0–210 wt.%) and solid-to-liquid (S/L) ratios (0.70 and 0.75) on the electromagnetic, thermal, and mechanical performance of metakaolin-based SMGCs. Fe addition improved magnetic permeability and reduced coercivity, with both remaining relatively steady within a narrow band at higher Fe contents. Saturation magnetization increased with Fe content and was further enhanced at lower S/L ratios due to improved Na⁺ mobility. Thermal conductivity increased and specific heat capacity decreased, indicating reduced volumetric heat-storage capacity and enhanced conductive heat diffusion. Electrical resistivity decreased and dielectric response increased with higher Fe and lower S/L ratios, reflecting changes in electrical conduction and polarization behavior. Mechanical strength also improved due to effective crack deflection and a dense matrix structure. The S75-F150 mixture achieved the best balance of functional and structural properties. These results highlight the combined effect of Fe content and mix design in tuning the multifunctional behavior of SMGCs for induction-driven energy applications. • Soft magnetic geopolymers enable efficient induction heating for energy-responsive infrastructure. • Fe powder boosts magnetic response while maintaining structural durability. • Solid-to-liquid ratio governs Na⁺ mobility and enhances magnetization dynamics. • Optimized mix design improves heat transfer and lowers electrical resistance. • SMGCs meet strength standards for electromagnetic pavement infrastructure.