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To solve the serious electromagnetic radiations and provide a new application for low-quality fly ash (FA), FA was used as the cement replacement for enhancing the electromagnetic absorption of cement-based composites. The microstructure and electromagnetic parameters of FA were characterized by means of scanning electron microscope and vector network analyzer, respectively. The results showed FA has the potentialities for wave attenuation due to its complex components and porous structure. However, the pozzolanic activity and packing effect of FA has a negative effect on the absorbing properties of FA/cement. In contrast, the absorbing properties can be enhanced greatly by introducing expanded polystyrene and FA in cement composites together. The dielectric absorbents are more suitable than conductive powders for wave attenuation in FA/cement composites. When the specimen consists of 25% FA & 50% EPS & 6% MnO 2 , the bandwidth of reflection loss less than −8 dB is enlarged to 10.95 GHZ with a peak value of −15.2 dB at 5.5 GHz.

To solve more and more serious electromagnetic radiations, cement-based composites were prepared by introducing porous materials into cement. The reflection losses were studied using arched testing method in the frequency range of 1.7–18 GHz. The results showed that the absorption properties were improved obviously. The mechanisms of wave attenuation of the composites were discussed, which indicated that the scattering and multi-scattering in porous beads played an important role. The filling ratio of porous beads, the bead geometries as well as the conformation of cement all had noticeably influence on the absorption properties. The lowest reflection loss of −22 dB was obtained at 5.6 GHz when the specimen was filled with 50 vol.% expanded polystyrene, and the effective absorption bandwidth (less than −10 dB) reached 10.6 GHz when the specimen was filled with 50 vol.% expanded polystyrene and 2 vol.% carbon black.