Geometry-regulated electromagnetic absorption of cement-based composite structures: a simulation-based scaling and mechanism study

Electromagnetic absorption in cement-based composites is commonly improved by modifying material composition, but such approaches may be constrained by workability, mechanical performance, durability, and cost. This study investigates the geometry-regulated electromagnetic absorption of cement-based pyramidal composite structures through a controlled simulation-based approach. Instead of developing a new material formulation, a literature-calibrated mechanism-decomposed dielectric response model was used to provide a fixed frequency-dependent dielectric input for a 2 wt.% carbon-black cement-based composite. Based on this unified material input, periodic electromagnetic simulations were conducted over 1–18 GHz to compare linear, nonlinear, and hollow pyramidal configurations. The results indicate that structural geometry can substantially influence reflection loss, absorption bandwidth, and characteristic absorption frequency under the assumed simulation conditions. For linear pyramids, the pyramid height mainly governs the average absorption intensity and deep-absorption bandwidth, whereas the periodicity primarily controls the centroid frequency. Nonlinear sidewall curvature improves absorption by redistributing the geometric gradient and modifying the internal energy-dissipation region under fixed external dimensions. Hollow pyramids show a threshold-dependent redistribution of absorption bandwidth, where the deep-absorption bandwidth is enhanced while the conventional effective bandwidth is slightly reduced. Geometry-based scaling descriptors further suggest that absorption strength and frequency position can be correlated with effective dissipation and characteristic length scales within the investigated parameter ranges. These findings provide simulation-derived design references for geometry-oriented regulation of metal-backed cement-based electromagnetic absorbing structures under fixed material conditions. The proposed descriptors help clarify how geometric parameters influence absorption strength and frequency response within the investigated parameter range.