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Electromagnetic interference shielding effectiveness of multi-cracked strain-hardening cementitious composites (SHCC)

Kim Soonho, Jang Yun Sik, Oh Taegeun, Lee Seung Kyun, Yoo Doo-Yeol

Archives of Civil and Mechanical Engineering

2023

Vol. 23, no. 3

art. no. e179, 2023

With the rapid increase in the use of wireless electronic devices, electromagnetic pollution has been recognized as a serious threat. There has been an increasing demand for the use of cement composites as electromagnetic shielding materials. Thus, this study investigated the advantages of adding a small dosage of carbon fibers to enhance the mechanical and electrical properties of strain-hardening cementitious composites (SHCCs) containing steel fibers. In addition, the effect of microcrack formation on the electromagnetic interference (EMI) shielding effectiveness of the SHCCs was analyzed. For this purpose, four different residual tensile strains were applied in preloading tests in the range of 0.015–0.1%. The test results suggested that the tensile performance of the SHCCs was improved by adding 0.2 vol% carbon fibers. Moreover, the rate of increase of the energy absorption capacity was higher (50%) than those of the tensile strength and strain capacity. The electrical conductivity and EMI shielding effectiveness of the SHCCs were noticeably increased by the addition of carbon fibers. The highest shielding effectiveness of 45.6 dB, at 1 GHz, was achieved for the SHCC containing 2% steel fibers and 0.2% carbon fibers, which was approximately 6% higher than that of the corresponding plain SHCC with only steel fibers. An approximately 44–47% lower shielding effectiveness was observed with the formation of through microcracks; however, the number of cracks and the residual tensile strain did not significantly influence the shielding effectiveness. This study can be a basis for evaluating EMI shielding effectiveness of damaged structures.

Influence of chemically treated carbon fibers on the electromagnetic shielding of ultra-high-performance fiber-reinforced concrete

Yoo Doo-Yeol, Kang Min-Chang, Choi Hong-Joon, Shin Wonsik, Kim Soonho

Archives of Civil and Mechanical Engineering

2020

Vol. 20, no. 4

367--381

The effects of carbon fiber and its surface treatment through chemical solutions on the mechanical properties and electromagnetic (EM) shielding of ultra-high-performance fiber-reinforced concrete (UHPFRC) were analyzed. Three types of carbon fibers chemically treated with sodium hydroxide, nitric acid, and ammonia solutions were evaluated, along with a plain carbon fiber control sample, at two different concentrations of 0.1% and 0.3% by weight. The surface of carbon fiber was oxidized by chemical solutions. The conductivity of UHPFRC increased with increasing the carbon fiber content, and slightly better conductivity was obtained using the chemically treated carbon fibers than plain fibers at the lower content of 0.1 wt%. Both steel and carbon fibers were effective at improving the shielding effectiveness of ultra-high-performance concrete, and a higher shielding effectiveness was achieved for higher carbon fiber content. Surface treatment using the nitric acid solution was the most effective at enhancing the tensile performance and EM shielding effectiveness, and the best shielding effectiveness (49.0 dB at 1 GHz) was achieved for UHPFRC with 0.1 wt% nitric acid treated carbon fibers. The shielding effectiveness was found to be generally proportional to the electrical conductivity, although its increase was minor relative to that of the conductivity.