Electromagnetic shielding performance and mechanical properties of vermiculite-based lightweight geopolymer mortars

In recent years, the widespread use of electronic devices has led to an increase in electromagnetic pollution, which causes electromagnetic interference and reduces the performance of systems. Furthermore, increasing electromagnetic pollution can pose serious risks to human health. This study investigates the development of vermiculite-reinforced lightweight geopolymer composites for protection against electromagnetic pollution. The composites were produced using F-class fly ash and vermiculite in varying proportions between 0 and 100%, along with 10-13 M NaOH solutions. The electromagnetic performance of the 160 × 140 × 40 mm tablet samples is evaluated by measuring S11, S21, and shielding effectiveness (SE) for 3-40 GHz frequency bands, 16 GHz and 32 GHz used as representative points for cross-property plots. While electromagnetic SE was characterized across the broad 3-40 GHz band, the frequencies of 16 GHz and 32 GHz are selected as representative points for detailed cross-property analysis and surface plotting to illustrate the interaction between mechanical and electromagnetic performance. 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) is obtained with 25% vermiculite and 11 M solution, while the highest compressive strength (30-32 MPa) is 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.