Enhanced Electromagnetic Wave Absorption in Plastic Composite Bricks with Hollow Pyramidal Surface Modification

The increasing presence of wireless technologies in modern infrastructure has intensified environmental exposure to electromagnetic (EM) waves which raise public health concerns and drive demand for construction materials that are able to absorb EM radiation. This study introduces plastic composite bricks incorporating hollow pyramidal surface structures to enhance microwave absorption across the 1–12 GHz range. Bricks were fabricated using a sustainable blend of polyethylene terephthalate (PET) and palm oil fuel ash (POFA), cement, and sand, with PET and POFA partially substituting sand and cement, respectively. In this study, PET was used to replace 10% of the sand by volume, and POFA was used to replace 30% of the cement by volume. Four surface configurations were investigated: Commercial brick (CB) and solid brick (SB) as a control brick, single hollow pyramid (SM1), and four-array hollow pyramids (SM2). Reflectivity was evaluated via CST Studio Suite simulations and validated experimentally using the NRL arch free-space technique at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0^{\circ}$</tex> incidence angles. Both SM1 and SM2 exhibited significantly reduced reflectivity compared to commercial and unmodified bricks. These findings highlight the potential of geometrically engineered sustainable composite bricks for mitigating EM wave exposure in built environments.