Effect of PET and POFA incorporation on microwave absorption of porous cement bricks

The growing reliance on wireless infrastructure and increasing electromagnetic pollution is prompting the development of building materials that are both multifunctional and environmentally sustainable. Conventional cement bricks are less capable of absorbing electromagnetic waves and are highly dependent on non-renewable resources. This study examines the microwave absorption performance of porous cement bricks using recycled polyethylene terephthalate (PET) as a partial sand replacement and palm oil fuel ash (POFA) as a partial cement replacement. Two experimental brick formulations, PB1 (65% cement, 30% POFA, 5% PET, foam) and PB2 (65% cement, 30% POFA, 20% PET, foam), were developed and evaluated alongside commercial cement bricks (CB). The electromagnetic properties were studied using the NRL free-space arch method at frequencies of 1 to12 GHz for vertical (10 cm thickness) orientations at 0°, 30°, and 60°. Band-specific analysis (L, S, C, X) shows that PB1 and PB2 exhibit enhanced microwave absorption compared to CB, with PB2 achieving the highest absorption of -30.17 dB in the C-band and exhibiting the lowest dielectric constant (ε=2.53). This enhancement is attributed to the increase in PET and porosity, which promotes interfacial polarization and impedance matching. These findings highlight the potential and environmental impact of waste-derived PET and POFA for sustainable and high-performance electromagnetic shielding in construction materials.