3.1.2. Dielectric Constant, Dielectric Loss and Tangent Loss/Tan Delta

Figure 2c,d show the resulting values of dielectric constant (*εr*) and dielectric loss (*εr* ) for different GRGC specimens when measured at different frequencies. The incorporation of GO in the geopolymer mix leads to higher (*εr*) and (*ε<sup>r</sup>* ) values of (10−5–10−4) and (10−4–10−3) at low frequencies, respectively. Both (*εr*) and (*ε<sup>r</sup>* ) show a significant decrease with the increase in frequency initially. However, the decrease rate of (*εr*) and (*ε<sup>r</sup>* ) was reduced at a higher frequency range and reached an approximately constant value. This phenomenon of the dielectric properties of GRGC specimens can be attributed to the polarization relaxation of molecules in the GRGC matrix. Initially, at lower frequencies, the molecules in the matrix have sufficient time and start orienting in the direction of the applied current. Consequently, at higher frequencies, the re-orientation is limited due to which the values of both (*εr*) and (*ε<sup>r</sup>* ) are reduced drastically [21]. The polarization of the molecules can be firmly influenced by different aspects of the geopolymer mix, i.e., alumino-silicate gel, unreacted particles, impurities available in the composite mix, etc. A study by Hanjitsuwan et al. observed a similar phenomenon and described the rationale as electrode/specimen interfacial polarization and double-layer polarization [17,18]. Alternative polarization mechanisms include ionic, dipolar or molecular, electronic and atomic mechanisms [22].

The (*D*) curves for the GRGC specimens are exhibited in Figure 2e. The (*D*) curve peaks ranged between 3.06 and 12.7 and ought to be related to the trend of the dielectric properties. However, GRGC3 obtained the highest (*D*) value: 10<sup>1</sup> Hz. The (*D*) values decreased with an increase in frequency, and the curves became almost constant at higher frequencies for all GRGC specimens. This exception can be closely related to the compactness of the specimens and the function of GO in enhancing the strength of the composites primarily via their pore-filling characteristics. Earlier investigations also indicated the limit of GO (0.1–0.3 wt.%) in improving the strength of geopolymer composites, as higher dosages tend to decrease the compactness due to the consequence of agglomeration [16,23–26].
