Self-Sensing of ECC Subjected to Flexural and Direct Tensile Loads Injected with Carbon Nanotubes and Reinforced with Mechanical Fibers

Abstract Research today aims to transform the cementitious system, in whole its forms, from a non-functional structural system into a smart system that can serve various civil facilities and infrastructure. One of the important applications in this field is the early detection of damage to the concrete structure before it develops by injecting the simple cementitious system with functional fillers capable of forming an electrical network inside it that can capture different scenarios of applied loads. This may include direct tensile loads and the flexural strength of mortar samples made from a cementitious matrix infused with multi-walled carbon nanotubes (MWCNT) and reinforced with polyvinyl alcohol fibers (PVA) in one instance and nylon fibers (NF) in another. The study examines different curing durations: 28, 56, 90, and 180 days at room temperature with water. To advance prior research and address a portion of the existing gap, the conventional matrix was infused with carbon nanotubes at a concentration of 0.5 by weight of cementitious components, alongside one of the reinforcement fibers (PVA) or (NF) at a consistent rate of 2% of the total volume of the mixture, maintaining this dosage throughout the investigation. A plain matrix devoid of additives was also established for comparative purposes. The results indicate the high mechanical behavior of the innovative alloys under the proposed loading scenarios; the CNT0.5PVA2 matrix proved its mechanical superiority over both the reference and innovative alloys, with improvement ratios under flexural strength for ages 28, 56, 90, and 180 days being 162%, 142%, 128%, and 103%, respectively. At the curing ages of 28, 56, 90, and 180 days, respectively, the improvement ratios under direct tensile strength were 10%, 5%, 5%, and 15%. The CNT0.5NF2 matrix excelled in its damage sensing ability with self-sensing values reaching 170 and 200% under direct bending and tensile loads, respectively.