Shielding effectiveness of concrete with graphite fine powder in between 50MHz to 400MHz

The shielding effectiveness (SE) of building materials is of concern due to the possibility of electromagnetic interference on sensitive equipment located inside the building. The SE of building material could be obtained directly using measurement but it requires expensive and elaborate setup. Alternatively, analytical method is preferable to predict the SE of building material for various conditions regarding the parameters to be evaluated such as thickness, moisture content, percentage of conducting materials added and so forth. Since most of the building materials are non-magnetic, its relative permittivity will be an important parameter for SE calculation. The effective permittivities of the concrete samples between 50 MHz to 400 MHz are measured using a TEM parallel plate. In this work, the SE of concrete samples are compared for various concentrations of graphite fine powder. It is found that a concrete of thickness 20 cm with 12wt% of graphite fine powder is able to provide a maximum of 2.4 dB additional shielding at 360 MHz. It is also observed that reflection loss is the dominant mechanism that contributes on the SE of a concrete with graphite fine powder.