Abstract
This study aims to investigate the relationship between the steel fibers and the electromagnetic wave shielding effectiveness of a high-performance fiber-reinforced cementitious composite (HPFRCC). The distribution characteristics of the steel fibers and the variation of the electrical conductivity of HPFRCC as a function of the fiber content were quantified based on micro computed tomography (CT) and impedance measurements to determine their correlations with the electromagnetic shielding effectiveness. The impedance results showed that no electrical network was formed in the composite by the steel fibers and it is difficult to manufacture HPFRCC with high-electrical conductivity using steel fibers alone without CNTs or other carbon-based materials. For the steel fiber content of greater than 0.5%, the number of contact points between the steel fibers increased significantly, and the relationship between the fiber content and the number of contact points was observed. Despite the improvement of the electrical conductivity owing to the presence of the steel fibers and to the increase in the contact points between the steel fibers, the shielding effectiveness did not increase further for the steel fiber contents equal or above 1.5%. Consequently, it was found that the factor that controls the shielding effectiveness of HPFRCC is not the electrical network of the steel fibers, but the degree of the dispersion of the individual steel fibers.
Highlights
The popularity of electronic devices and their use, especially in wireless and communication systems, has resulted in problems, such as pollution attributed to electromagnetic interference (EMI)and information security violations that are (a) harmful to human health and (b) impose risks associated with the leakage of military secrets [1]
The distribution characteristics of the fibers and the variation of the electrical conductivity of high-performance fiber-reinforced cementitious composite (HPFRCC) as a function of the fiber content were quantified based on micro computed tomography and impedance measurements to determine their correlations with the electromagnetic shielding effectiveness
SF2.5 sample was 5000 Ω·cm, which is much higher than the resistance of 200 Ω·cm of HPFRCC mixed with carbon nanotubes (CNTs) reported in a previous study [22]. This indicates that no electrical network was formed in the composite by the steel fibers. This result shows that it is difficult to manufacture HPFRCC with high-electrical conductivity using steel fibers alone without CNTs or other carbon-based materials
Summary
The popularity of electronic devices and their use, especially in wireless and communication systems, has resulted in problems, such as pollution attributed to electromagnetic interference (EMI)and information security violations that are (a) harmful to human health and (b) impose risks associated with the leakage of military secrets [1]. To mitigate the electromagnetic interference pollution problems, it is essential to develop electromagnetic shielding materials that act as barriers to limit the penetration of electromagnetic waves by reflection or absorption [6]. Concrete is the most representative structural material, it is known to have extremely low electromagnetic wave shielding effectiveness compared with other shielding materials because of its low electrical conductivity (less than 1 × 10−5 S/cm). Concrete is a nonconductor, studies are being conducted to improve its shielding effectiveness to prevent harmful effects from electromagnetic waves. To enhance the shielding effectiveness of concrete, conductive materials such as carbon nanotubes (CNTs) and steel fibers are mixed during the mixing stage, in which an appropriate amount of these materials is mixed with concrete to improve its shielding effectiveness
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