Evaluation of Various Factors on Electrical Properties of GNP-Reinforced Mortar Composites

Graphene nanoplatelets (GNPs) have the same chemical structures as carbon nanotubes but their internal structure consists of multiple layers of graphene with thicknesses of only a few nanometers. Due to their increased thickness, GNPs are less prone to agglomeration and entanglement when they are used as nanofillers in composite materials. Although it has been shown that self-sensing cementitious composites can be fabricated using GNPs, further studies are needed to reveal effect of various factors on the performance of such composites. Here, a fabrication method that mainly employs polycarboxylate-based superplasticizers together with high-speed shear mixing to disperse GNPs in cement composites is used to prepare GNP-reinforced mortar composites. The molecular structure of polycarboxylate-based superplasticizer can considerably affect the performance of GNP-cement composites. Therefore, two commercially available polycarboxylate-based superplasticizers that possess varying backbone and side-chain lengths are systematically incorporated to prepare GNP-reinforced multifunctional composites. In addition, the effects of mixing durations on the electrical properties of the developed composites are assessed. Another essential challenge in the development of multifunctional cement composites is to improve the interfacial interaction between GNPs and the hydration products of cement such as calcium-silicate-hydrates (CSH). Here, incorporation of supplementary materials such as silica fume into the matrix is studied to improve the bond between a cementitious matrix and nano reinforcement. The bulk resistivity of the mortar specimens is measured using the four-probe measurement method. The piezoresistive behavior and sensing ability of the GNP-reinforced mortar composites are investigated through compressive tests at quasi-static.