Nanosensors for nanoscale structural health monitoring in civil engineering: new insight on carbon nanotubes devices
Résumé
Nanoporosities play a most significant role in the durability of cementitious materials, so that nanoscale features are a promising target for structural health monitoring (SHM). However, to this day, no sensor features the resolution required to investigate non-destructively these features. To fill in this loophole, IFSTTAR is devising innovative nanoscale SHM solutions based on nanosensors. Two types of carbon nanotubes (CNT) devices are being studied: ultrasonic nanotransducers for microporosity assessment and field-effect transistors for relative humidity (RH) monitoring. A detailed numerical model of the CNT-based ultrasonic nanotransducers we are devising shows that upon embedding in a cementitious material it could determine the volume and content of the porosity in its vicinity. Such information would be invaluable in the evaluation of structural durability (Lebental et al., 2011). Our characterizations of the field-effect transistors devices we fabricated with low density CNT networks indicate that they could be exploited as a high sensitivity means to probe high RH environment such as concrete (Bondavalli et al., 2009) With such promising outputs, these two studies open up the path toward in-situ morphology and composition monitoring of the microporosity of cementitious materials by nanosensors. This nanosensors-based nanoscale knowledge is the key to detect and prevent degradations of cement-based structures. As such, it will significantly contribute to an improved sustainability in civil engineering.