Electromagnetic Shielding Performance and Mechanical Properties of Vermiculite-Based Lightweight Geopolymer Mortars

The widespread use of electronic devices causes electromagnetic interference, which increases electromagnetic pollution, reduces system performance, and may pose health risks. This study investigates the development of vermiculite-reinforced lightweight geopolymer composites for electromagnetic shielding purposes. The composites were produced using F-class fly ash, vermiculite ratios ranging from 0 to 100%, and 10–13 M NaOH solutions. The electromagnetic performance of the 160×140×40 mm tablet samples was evaluated by measuring S11, S21, and shielding effectiveness (SE) at 16 GHz and 32 GHz frequency bands. All mixtures showed good impedance matching with reflection values below − 10 dB. SE results show that V25–M12, V50–M12, and V100–M12 mixtures, especially in the Ka band, provided high electromagnetic attenuation by exhibiting resonance peaks above 50 dB. The increase in vermiculite content reduced the bulk density by 8–17% due to its porous structure. Higher molarities (especially 13 M) created a looser microstructure. The highest mechanical flexural strength (8.9 MPa) was obtained with 25% vermiculite and 11 M solution, while the highest compressive strength (30–32 MPa) was obtained with the vermiculite-free control sample. Taguchi analysis showed that the combination of 25% vermiculite and 11–13 M NaOH provided the most balanced mechanical and electromagnetic performance.