Evaluation of fracture toughness in graphene-based cementitious nanocomposites via electrical impedance

Abstract

The present work investigates experimentally the improvement of fracture toughness and electrical conductivity in the hardened cementitious matrix after the addition of graphene nanoplatelets (GnPs), at four different concentrations varying between 0.05 wt% and 0.4 wt% per cement. The experimental investigation is conducted through flexural and electrical impedance spectroscopy (EIS) tests on prismatic specimens. The study is oriented towards establishing a correlation between the electrical response of the nanocomposites under alternate current and the exhibited fracture toughness values (KIc). The flexural test results show that the incorporation of the GnPs in the matrix can increase the average KIc values and can decrease the average resistivity (ρ) when compared with the reference matrix. The maximum increase in KIc (+ 29 %), and the decrease in ρ (- 68 %) were found in the mixture with the lowest amount (0.05 wt%) of GnPs. Moreover, the comparison of the ρ values and the KIc values, as a function of the GnPs concentration, reveals a reverse relation between the two parameters (KIc and ρ). The functional correlation between these parameters was also confirmed by linear regression analysis, resulting from the experimental data fitting. The analysis provides evidence that EIS can be used as a non-destructive tool to assess the fracture toughness of cementitious nanocomposites.