Evaluating the Self-Sensing Ability of Cement Mortars Manufactured with Graphene Nanoplatelets, Virgin or Recycled Carbon Fibers through Piezoresistivity Tests

This paper presents the resistivity and piezoresistivity behavior of cement-based mortars manufacturedwithgraphenenanoplateletfiller(GNP),virgincarbonfibers(VCF)andrecycledcarbon fibers (RCF). GNP was added at 4% of the cement weight, whereas two percentages of carbon fibers werechosen,namely0.05%and0.2%ofthetotalvolume. Thecombinedeffectofbothfillerandfibers was also investigated. Mortars were studied in terms of their mechanical properties (under flexure and compression) and electrical resistivity. Mortars with the lowest electrical resistivity values were also subjected to cyclic uniaxial compression to evaluate the variations in electrical resistivity as a function of strain. The results obtained show that mortars have piezoresistive behavior only if they aresubjectedtoapriordryingprocess. Inaddition,dryspecimensexhibitahighpiezoresistivityonly when loaded with 0.2 vol.% of VCF and 0.4 wt.% of GNP plus 0.2 vol.% RCF, with a quite reversible relation between their fractional change in resistivity (FCR) and compressive strain.