Flexural stress and crack sensing capabilities of MWNT/cement composites

The flexural stress/crack sensing capabilities of multi-wall carbon nanotube (MWNT)/cement composite sensors were investigated in this study. The electrical/mechanical characteristics of the composites were explored with respect to the MWNT contents, prior to evaluating the sensing capabilities of the composites. A dramatic increase (over three orders) in the electrical conductivity, compressive and flexural strength (36% and 18%) were observed in the composite specimens. The sensing capabilities of the composites were evaluated by monitoring the electrical resistance change of the composites under loading. The composites subjected to flexural stress showed higher sensing capability as the MWNT content was increased. Both stress and crack sensing capability were enhanced with the increase of MWNT content. In addition, the examination demonstrated that an embedment of MWNT content of 0.6 wt% resulted in the best sensing capabilities. Lastly, the composites were embedded in two different locations of reinforced mortar beams for in-situ monitoring of electrical resistance. A dramatic change in the resistance of the composites were accompanied at failure of the mortar, regardless of the sensor location. The obtained result may have implications for the use of the composites as a stress/crack sensor in cement-based composite structures.