Design and preparation of double-layer structured cement-based composite with inspiring microwave absorbing property

Abstract

Double-layer structured cement-based composites, including matching layer and loss layer, were designed and fabricated. Matching layer composed of hollow glass microspheres was used to improve the impedance matching of cement-based composites and attenuate microwaves through complicated channels. Loss layer made up of single-particle sand (1.25–2.5 mm) and carbon powder absorber were designed to absorb microwaves by porous structure and resistive losses. It was found that the absorbing properties of cement-based composites were significantly improved by using the double-layer structure design. For the cement-based composite containing 10 wt% hollow glass microspheres in the matching layer (thickness = 20 mm) and 3 wt% carbon powder in the loss layer (thickness = 10 mm), the reflectivity was below −9 dB in the whole testing frequency ranges and the lowest reflectivity was −12.4 dB at 8.9 GHz, and the absorption bandwidth below −10 dB was 5.2 GHz in the frequency ranged 8–13.2 GHz. The compressive and flexural strength were higher than 42.5 MPa and 4.6 MPa, respectively. In comparison with the ones in literature, the fabricated double-layer structured cement-based composites showed excellent mechanical strength at the same microwaves absorbing level.