Self-Sensing Mortars with Recycled Carbon-Based Fillers and Fibers

This work investigates the potential of recycled carbon-based materials, obtained from industrial by-products, for the production of Multifunctional Cement-based Composites (MCC) with self-sensing behavior, usable in Structural Health Monitoring (SHM) systems. As recycled materials, Used Foundry Sand (UFS) and Recycled Carbon Fibers (RCF) have been chosen, whereas Graphene Nanoplatelets (GNP) and Virgin Carbon Fibers (VCF) have been selected as reference industrial fillers and fibers, respectively. Their effects on OPC-based mortars have been tested in terms of mechanical strength (compressive, flexural), durability (water absorption), microstructure (porosity), electrical and piezoresistive behavior (resistivity in static and under-load conditions). The results show that the combination of recycled fillers-fibers gives the best results in terms of workability, microstructure, strength, and durability. The worst compressive performances obtained with GNP are related to its hydrophobicity and the related problems in mixing. On the other hand, mixtures with UFS show a low electrical conductivity, but a high sensitivity to deformation (electrical strain-sensing). High-carbon by-products could be a functional, low-cost, and eco-friendly solution to produce high-performance and conductive concretes for self-monitoring systems.