Table 3 shows that the EMI shielding effectiveness (i.e.,
attenuation upon transmission) is increased monotonically
by increasing the fly ash proportion, while the attenuation
upon reflection is decreased slightly and monotonically,
whether the frequency is 1.0 or 1.5 GHz. This means that
the fly ash enhances the shielding through enhancing the
reflectivity. On the other hand, silica fume improves the
shielding effectiveness only marginally at either frequency