Damage Detection Using Smart Concrete Engineered with Nanocomposite Cement-Aggregate Interfaces

Self-sensing or "smart" cementitious composites, in which its electrical properties are sensitive to stress/strain, cracks, or damage, have gained considerable attention. Its design is based on mixing conductive additives (e.g., fibers or nanotubes) in the cement matrix. However, these additives degrade the intrinsic properties, increase costs, and reduce workability. Thus, this study sought to devise an alternate form of smart cementitious composite by modifying the cement-particle interface with multi-walled carbon nanotube (MWNT)-based thin films. This design significantly reduced the amount of MWNTs used (thus costs) and had minimal impacts on mix work-ability. Here, MWNT-based films were airbrushed onto dried fine aggregates, which were then used for casting mortar specimens. Previous work showed that its electrical properties were sensitive to strain and damage. In addition, an electrical impedance tomography (EIT) spatial conductivity mapping algorithm was implemented. Because EIT could map a material's spatial conductivity, and the smart mortar's electrical conductivity scaled with damage, the technique enabled the detection of damage severity and its location. Several experiments were conducted for validation.