Electromagnetic interference shielding of multi-cracked high-performance fiber-reinforced cement composites - Effects of matrix strength and carbon fiber

High-performance fiber-reinforced cement composites (HPFRCC) can be adopted as a building material for electromagnetic interference (EMI) shielding due to its high-volume content of conductive steel fibers incorporated. Structures made of HPFRCC are, however, highly possible to have very tiny microcracks, formed by environmental factors, so that the relationship between the crack areas and the EMI shielding effectiveness needs to be evaluated. For this, two different matrix strengths of 100 and 180 MPa and two different volume contents of carbon fibers, i.e., 0.1, and 0.3%, were considered, and various cracking areas in the HPFRCC were intentionally created in this study. The lower-strength composites provided better shielding effectiveness as compared to the higher-strength composites for both the non- and multi-cracked states due to a presence of iron(III) oxide and smaller silica fume contents. The addition of 0.3% carbon fibers was effective on improving both the electrical conductivity and shielding effectiveness of HPFRCC. The efficiency of carbon fibers on the shielding effectiveness increased at higher frequencies and micro-cracked states. The shielding effectiveness of HPFRCC was deteriorated with increased total crack area ratio that is from the multiple microcracks and macro localized cracks. The biggest reduction rate of the shielding effectiveness in the multi-cracked HPFRCC was found to be 23% at the modulus of rupture point as compared with the non-cracked counterpart. Such a deterioration of EMI shielding effectiveness of HPFRCC by crack formation needs to be thus considered in its practical application. (C) 2020 Elsevier Ltd. All rights reserved.