Carbon nanotubes (CNTs) are incredibly versatile in their applications. One such exciting application in recent years has been the development of CNT-modified cement-based smart materials (CNT-CS). These utilise the electromechanical properties of CNTs to expand the uses of cement from a purely structural component to a smart material that can act as a sensor, revolutionising structural health monitoring (SHM).

Structural Health Monitoring

Structural health monitoring ensures the safety, longevity, and integrity of infrastructure, such as buildings and bridges, by using sensors to continuously monitor the condition of the structure and detect any damage. Traditionally, this process has involved the use of sensors attached to or embedded in the concrete, however, these suffer from a short lifespan, compatibility issues with concrete, and problems with interference. The development of CNT-CS materials has the potential to transform structural health monitoring, providing increased sensitivity and incorporating a self-monitoring capability into concrete structures.

The Use of CNTs as Piezoresistive Sensors

CNT-CS materials are produced through dispersing CNTs within cement to form conductive concrete. The addition of CNTs to cement not only improves various properties of the cement, including strength, conduction, and wave-absorbing properties, but also enables its use as a sensor, with great potential for use in SHM.

The use of CNT-CS in SHM relies on their piezoresistive and piezoelectric properties. Piezoresistivity is the change in the electrical resistance of a material when it undergoes strain or stress. Piezoelectricity is the ability of a material to generate an electric charge when it undergoes mechanical stress. Together, these properties enable CNT-CS to act as an intrinsic sensor within concrete structures, enabling the monitoring of stress and strain in real-time and the detection of small cracks, enabling problems to be detected and resolved before they develop into serious issues.

Research into the use of CNT-enhanced concrete to produce buildings, roads, and bridges that can monitor their own structural health is ongoing, but offers great potential for transforming the future of infrastructure.

For more details, check out this great review article in the link below.

Piezoresistive/piezoelectric intrinsic sensing properties of carbon nanotube cement-based smart composite and its electromechanical sensing mechanisms: A review