Self-sensing performance of cementitious composites with functional fillers at macro, micro and nano scales

Self-sensing cementitious composites have attracted substantial attention as a multifunctional construction material for structural health monitoring (SHM). This study aimed to develop self-sensing cementitious composites using a combination of macro, micro and nanoscale conductive fillers, as the hybrid fillers can take advantage of different types of conductive fillers and create a synergistic effect. Magnetite aggregate (MA), carbon fibre (CF) and carbon nanotube (CNT) were combined and used as the conductive fillers for the fabrication of self-sensing cementitious composites, where the mechanical properties, electrical properties and piezoresistive performance were studied. The MA at 100 wt% achieve the optimal mechanical properties, leading to a 5% increment in compressive and a 25% increment flexural strength with a value of 37.3 and 5.7 MPa. Additionally, multiple reinforcing effects were achieved when combining different types of functional fillers, which a single filler cannot achieve. The best conductive filler combination is MA, CF and CNT hybridisation, each at 100, 0.3 and 0.05 wt%, respectively. A 17% improvement in terms of compressive strength can be observed. And the piezoresistive response can achieve a maximum fractional change in resistivity of 44.7% and demonstrates enhanced linearity, repeatability, signal to noise ratio and stability.