Effect of electric arc furnace slag and magnetite materials on EMI shielding properties of cementitious composites

To impart electromagnetic interference (EMI) shielding in cementitious composites, electrically conductive and electromagnetic absorbing additives are generally used. This research examined the effect of adding electric arc furnace slag (EAFS) or heavyweight aggregates (HWA), alone and in combination with carbon fibre (CF), on the EMI shielding properties of cementitious composites. Different percentages of both additives were added to a control mix to study the effect on mechanical properties, electrical conductivity and EMI shielding. Optimal shielding was produced for aggregate contents of 1.5 wt%, with values of 5.18 dB for the EAFS mixes and 3.25 dB for the HWA mixes, within the frequency range 30 MHz to 1.5 GHz. Hybrid mixes were fabricated using 0.7 wt% of 12 mm long CF and three different percentages of each aggregate. In combination with the CF, the optimal level of shielding was produced with EAFS and HWA contents of 1 wt%. These optimal shielding levels were 34.21 dB and 36.78 dB, respectively, within the 30 MHz to 1.5 GHz frequency range. A further increase in either type of aggregate produced a gradual reduction in EMI shielding effectiveness.