Effects of graphene nanoplatelets type on self-sensing properties of cement mortar composites

Abstract

Graphene nanoplatelets (GNPs) that possess high electrical conductivity and relatively low cost have been considered to obtain self-sensing capability in cementitious composites. However, there is limited understanding on the effects of physical properties of GNPs such as particle size and surface area on the self-sensing characteristics of the cement composites. In this study, nine types of GNPs that have different surface areas, particle sizes, and thicknesses are considered in the development of self-sensing mortar composites. For each type of GNPs, specimens with GNP concentrations of 2.5%, 5%, and 7.5% by weight of cement were prepared. The bulk electrical resistivity of the developed mortar composites was measured at different curing ages. The compressive strength of the specimens was also evaluated. The piezoresistive behaviors of the GNP-reinforced mortar composites were studied through cyclic compressive loading tests at different load levels. During piezoresistivity tests, the measurements were conducted through both direct current (DC) and alternating current (AC) and the results obtained from each method were evaluated. Results reveal that GNPs with very small particle sizes and large surface areas cannot disperse effectively in the cement matrix and do not provide piezoresistive characteristics. For GNPs with relatively smaller surface areas, the GNPs with higher particle sizes form effective conductive paths and exhibit better piezoresistive characteristics.