The electromagnetic characteristics of fly ash and absorbing properties of cement-based composites using fly ash as cement replacement

[Display omitted] . ► A new application of fly ash used for wave absorbing is explored. ► The multi-component and porous structure makes the potential of fly ash for wave attenuation. ► The pozzolanic activity of fly ash is harmful to wave absorbing. ► Absorbers with broader bandwidth based on cement/fly ash matrix are developed. 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.