Self-Sensing Characterization of GNP and Carbon Black Filled Cementitious Composites

Abstract

Over the past decades, a number of structural health monitoring methods have been developed for condition assessment of concrete structures. Most of these methods require the installation of external sensors. Accelerometers are commonly used for vibration-based damage detection for the entire structure, while strain gauges are installed in order to detect cracking and damage at the component level. Conventional strain sensors, such as metal foil strain gauges, have been widely used to monitor local conditions in concrete structures. However, all of these sensors have certain shortcomings such as exhibiting limited durability and low gauge factor, and providing only pointwise strain measurements. Multifunctional cement-based composites that can determine their own strain and damage can overcome the limitations of these traditional sensors. This study explores the use of two different nanomaterials, namely graphene nanoplatelets (GNP) and carbon black (CB) for the development of self-sensing cementitious composites and the synergetic effects in their hybrid utilization. A simple fabrication method that does not require special treating procedures such as ultrasonication for dispersing nanomaterials is pursued. Twelve batches of mortar specimens reinforced with only GNP or CB at different concentrations, or with both GNP and CB fillers are prepared. A polycarboxylate-based superplasticizer is used to disperse nanomaterials and to increase the workability of the nano-reinforced mortar. Scanning electron microscope (SEM) is utilized to assess the distribution quality of nanomaterials. Standard cubic specimens are tested for compressive strength at 28 days. The bulk resistivity of the standard prismatic specimens is measured using the four-point probe method. The piezoresistive response of nano-reinforced cement composites is evaluated under the cyclic compressive loads.