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

Abstract

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.

Review of the Effects of Supplementary Cementitious Materials and Chemical Additives on the Physical, Mechanical and Durability Properties of Hydraulic Concrete

“…EMI-absorbing concrete is more convenient than EM-reflecting concrete because the reflected wave may interact with the incident wave [ 291 , 292 ]. The electromagnetic shielding effectiveness of concretes with different chemical admixtures are given in Table 9 [ 271 , 293 , 294 , 295 , 296 , 297 , 298 , 299 , 300 , 301 , 302 , 303 , 304 , 305 ]. It can be observed from Table 9 that carbon-based materials are the main focused of electromagnetic shielding properties in concrete.…”

A Systematic Review of HPM Energy Absorbers for Building Applications

“…The shielding effectiveness of concrete samples containing graphite powder in various proportions was compared in [54]. A 20 cm thick concrete element containing 12% wt.…”

“…A 20 cm thick concrete element containing 12% wt. of graphite powder was found to increase shielding effectiveness (SE) by 2.4 dB at 360 MHz (see Figure 7, adapted from [54]). It was noted that reflection was the dominant mechanism acting on the shielding effectiveness of concrete with a graphite powder addition.…”

Effect of Incident Area Size on Estimation of EMI Shielding Effectiveness for Ultra-High Performance Concrete With Carbon Nanotubes

“…This assumption is made because the CNTs are not magnetic materials and cannot improve µ r [33]. Moreover, a carbon filler, e.g., CNTs, can significantly affect the relative conductivity σ r , whereas it has little effect on the relative permittivity ε r [12], [28], [34], [35].…”