Carbon nanotubes added to cement composites can act as stress/strain sensors or vibration sensors (piezo-resistivity). You will be able to get more information from the following references:

1) Han et al. : A self-sensing carbon nanotube/cement composite for traffic monitoring, NANOTECHNOLOGY, Vol. 20 No. 44 (2009)

2) Xun Hu and Eil Kwon: Carbon nanotube based self-sensing concrete for pavement structural health monitoring (2012). This document is available in pdf format from,  ntl.bts.gov/lib/45000/45000/45066/3789.pdf

Thank you very much Sivakumaran Wignarajah