UC San Diego

Concrete and other cementitious composites used in civil infrastructure are prone to many forms of damage. For example, cracks could occur and propagate to cause catastrophic component or system-level failure. Therefore, the objective of this study was to nano-engineer a self-sensing cementitious composite that could detect and locate damage. Integration of multi-walled carbon nanotubes (MWNTs) in the mortar mix design and during casting enhanced the electromechanical or sensing properties of the cementitious composites. Instead of directly dispersing MWNTs in the cement matrix, the cement-particle interface was modified using spray-coated MWNT-latex thin films deposited directly onto dry sand particles prior to mortar casting. This procedure preserved MWNT dispersions within the thin film architecture, used minimal amounts of MWNTs, was scalable, and provided dramatic sensing performance enhancements. The mechanical and electromechanical properties of mortar specimens were characterized using compressive cyclic load tests. Furthermore, an electrical resistance tomography (ERT) algorithm was used for mapping mortar specimens' spatial resistance distributions. Since their resistance was precalibrated to strain, localized changes in calculated resistance indicated damage. Spatial damage detection was validated by drilling holes in various locations in cementitious composite plates and then by mapping resistance distributions using ERT.