Development of structural carbon nanotube–based sensing composites for concrete structures

Structural health monitoring has become a viable solution to monitor critical infrastructure components that show distress or are unable to pass current load ratings. This research introduces the concept of a composite layer bonded to concrete structures, which is capable of providing distributed sensing capabilities. The layer consists of carbon nanotubes that are deposited on a carrier, which form a continuous conductive skin that is exceptionally sensitive to changes in strain and the formation and propagation of micro-damage and macro-damage. It can be either structural, where the layer represents the reinforcement as well as the sensor, or nonstructural, where the layer acts as a sensing skin alone. Distributed sensing allows for increased detectability of forming or growing damage that cannot necessarily be captured with conventional point-type sensors such as strain gages or accelerometers. Once developed, this sensing skin may be able to give real-time feedback on changes in strain, temperature effects, and formation and propagation of damage. In this article, we present the fabrication and evaluation of an integrated structural sensing composite layer attached to a concrete beam specimen. The specimen was tested to failure in the laboratory. Experimental results are presented and discussed, and currently ongoing research is introduced.