Development of Multifunctional Carbon Nanofiber Aggregate for Concrete Structural Health Monitoring

Fiber research in concrete construction is an ongoing field and the use of carbon nanofibers (CNFs) will be examined in this study. Short-fiber composites are a class of strain sensor based on the concept of short electrically conducting fiber pull-out that accompanies slight and reversible crack opening. For a fiber composite to have strain sensing ability, the fibers must be more conducting than the matrix in which they are embedded, of diameter smaller than the crack length, and well dispersed. Their orientations can be random, and they do not have to touch one another. The electrical conductivity of the fibers enables the DC electrical resistivity of the composites to change in response to strain damage, hydration level, or temperature, allowing sensing. Because of the high cost associated with CNFs, a CNF aggregate (CNFA) was developed. The CNFA is a 16.39 cm3 (1.00 in.3) cubic specimen of CNF mortar. The CNF mortar is self-sensing and can be used to determine the hydration level, damage, or temperature in the multifunctional CNFAs. The CNFAs can be embedded in reinforced or prestressed concrete structures and used to monitor early strength, determine the localized damage, or measure the temperature in a structure.