Influence of carbon fiber on the electromagnetic shielding effectiveness of high-performance fiber-reinforced cementitious composites

The significance of electromagnetic interference shielding is being increasingly emphasized in the construction field due to information security violation. This study investigated the mechanical performance, electrical conductivity, and electromagnetic shielding effectiveness of high-performance fiber-reinforced cementitious composite (HPFRCC) produced by incorporating carbon fibers. The carbon fibers were added to the HPFRCC at 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4 vol %. The electrical resistivity of the HPFRCC was measured by alternating current (AC) and direct current (DC) methods and the shielding effectiveness was measured in the shielding room in accordance with MIL-STD-188-125. The test results showed that the AC resistivity of the HPFRCC mixed with carbon fibers was strongly associated with the applied voltage. For measuring the real resistivity of the HPFRCC, the applied voltage should be more than the minimum voltage required for the current to pass through the electrical path in the cement matrix if the carbon fiber content exceeds the percolation thread (greater than 0.8% here). The compressive strength decreased with increase in the carbon fiber content owing to the reduced slump flow and resultant less compaction effect of HPFRCC. The relative permittivity results indicates that the shielding mechanism of the HPFRCC is likely to be electromagnetic reflection rather than electromagnetic absorption by the carbon fibers. It also clearly showed that the dominant factor affecting electromagnetic shielding of the HPFRCC is the amount of carbon fibers rather than the electrical conductivity resulting from continuous connection of carbon fibers.