Experimental investigation on mechanical and piezoresistive properties of cementitious materials containing graphene and graphene oxide nanoplatelets

Recent investigations show that graphene nanoplatelets (GNPs) and graphene oxide nanoplatelets (GONPs) are promising nano-sized additives to enhance the mechanical property and smartness of cementitious materials. To further delineate the collective effects of GNPs and GONPs, particularly their contents, on the performance of concrete, a comprehensive investigation is carried out in this study. Mortar samples, characterized by different water-cement ratios and containing different amounts of GNPs and GONPs, are experimentally tested to systematically probe their strength, electrical resistance and piezoresistive reactions. The results show that to take advantage of GNPs and GONPs, the water-cement ratio and associated workability of concrete are important. With a proper water-cement ratio, a small percentage of GNPs and GONPs can significantly improve the concrete strength, while the content of GNPs needs to be substantially increased to achieve low electrical resistance and accurate piezoresistive reaction. To understand the mechanisms of conductivity and piezoresistance at the micro-scale, micro-characterization utilizing Scanning Electrical Microscopy (SEM) equipped with Energy Dispersive Spectrometer (EDS) technique is performed to examine the mortar microstructure containing GNPs. In addition, rapid chloride corrosion test on the selected mortar samples shows that the migration of chloride ions slows down with the addition of GNPs in cement paste.