Sustainable electromagnetic interference shielding cement composites incorporating ball-milled iron mill scale for X-band applications

The widespread use of electronic systems in buildings has increased the demand for economical, sustainable, and compatible electromagnetic interference (EMI) shielding materials for structural applications. This study investigates the use of ball-milled waste iron mill scale (B-WIMS) as a partial substitute for manufactured sand in cement mortar for X-band (8–12 GHz) electromagnetic interference shielding. Mechanical ball milling refined the mill scale into a finer and more reactive form, promoting uniform dispersion and enhancing magnetic–dielectric interactions within the cement matrix. Mortar mixes containing 0–30% B-WIMS were produced and assessed for shielding effectiveness, microstructural characteristics, and cost efficiency. A progressive improvement in shielding performance was observed with increasing B-WIMS content, with B-WIMS30 achieving a maximum shielding effectiveness of 32.50 dB, corresponding to more than 99.9% attenuation of incident electromagnetic waves. Shielding was primarily governed by absorption, resulting in minimal reflection and transmission. SEM analysis revealed significant pore refinement and matrix densification compared with the control mortar. Cost evaluation showed only a marginal increase in production cost while significantly improving shielding performance.