PSI - Issue 42

E. Tziviloglou et al. / Procedia Structural Integrity 42 (2022) 1700–1707 Tziviloglou et al. / Structural Integrity Procedia 00 (2022) 000 – 000

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3.3. Relation between electrical resistivity and fracture toughness Furthermore, from the comparison of Fig. 4 and Fig. 5, it was observed that the graphical curves of the average values of ρ and K Ic as a function of the GnP content exhibit an almost reverse shape as seen in Fig. 6a. Therefore, by constructing another graph (Fig. 6b) that displays the 1/ ρ values (on the x-axis) over the K Ic values (on the y-axis) of the corresponding GnPs concentrations, a nearly linear relation between the two parameters was revealed.

Fig. 6. a. Comparison of fracture toughness and resistivity values with varying GnP content; b. Correlation between K Ic and 1/ ρ values and linear fitting curve for cementitious nanocomposites with varying GnP content. The equation that describes the functional relation between 1/ ρ and K Ic is given in Eq. 4, as: = 1.63 ∙ 1 + 0.724 . (4) Yet, the above equation expresses certain material and experimental parameters, such as nanofiller type and concentration, cement and SP type, w/c, dimensions of specimens, and other material and experimental features. This means that the x-coefficient (1.63), as well as the constant value (0.724) of the fitting equation are expected to change, when different nanomaterials and experimental features will be selected. However, it is evident that the EIS is a straightforward methodology that can be easily implemented to evaluate the fracture toughness of cementitious The fracture toughness and electrical resistivity of GnPs-reinforced cement pastes were investigated. The results showed that the addition of GnPs increased the fracture toughness of the cement pastes, while the lowest examined concentration (0.05 wt%) lead to a 29 % increase of fracture toughness. On the contrary, the electrical resistivity of the mixtures with GnPs exhibited an inverse response compared to fracture toughness. The electrical resistivity of the GnPs-modified pastes dropped significantly compared to the reference paste. The maximum drop of almost three times was shown by the mixtures with the lower examined GnPs concentrations (0.05 and 0.1 wt %). The experimental investigation indicated that there is a functional relation between the fracture toughness and the electrical resistivity obtained by alternate current measurements. Therefore, EIS can be used in cementitious nanocomposites as a valid, non-destructive tool to assess their fracture toughness. nanocomposites. 4. Conclusions