Mechanical and electrical properties investigation for electrically conductive cementitious composite containing nano-graphite activated magnetite

Electrically conductive cementitious composite (ECCC) is a multifunctional material utilized in structural health monitoring (SHM), electromagnetic shielding, and pavement deicing. The addition of nano-graphite (NG) in ECCC can prominently enhance the electrical behavior and improve the mechanical strength due to its filling of molecular pores. Besides, magnetite can replace part of graphite owing to its excellent mechanical performance. To enhance molecular dispersion and bring out the potential of the composite, three various modifying treatments were carried out. This paper explored the modifying effects of alkali excitation, ultrasonic vibration coating, and combined activation on magnetite-nano-graphite incorporated ECCC. In total, 360 ECCC specimens were proposed for electrical resistance, compression strength, and flexural strength. The results indicate that chemical activation facilitated the pozzolanic reactivity of fly ash-cement system. Meanwhile, the ultrasonic vibration prompted the uniform distribution of magnetite-nano-graphite. The combined surface treatment is superior to any single treatment, endowing ECCC balanced in great mechanical properties and electrical conductivity. A 6 wt% ratio of NG, 60 wt% of magnetite with combined activation is illustrated as the optimum design with 6.92 MPa of flexural strength, 46.75 MPa of compressive strength, and 3430 Ω cm of resistance. Finally, a microstructure analysis of ECCC was performed by SEM to investigate the conductive mechanism and a schematic diagram was proposed.