Self-monitoring of smart concrete column incorporating CNT/NCB composite fillers modified cementitious sensors

In this paper, cementitious sensors were fabricated with electrostatic self-assembled carbon nanotubes (CNT)/nano carbon black (NCB) composite fillers, and embedded into concrete columns to develop smart structural components. Self-sensing properties of the sensor/smart column were evaluated under cyclic loading and monotonic loading through measuring the fractional change in resistivity (FCR) of sensor. The effect of sensor on the mechanical strength of column was also studied. Experimental results showed that whether the sensor is embedded in concrete column or not, its piezoresistivity presents high stability and repeatability under cyclic loading within the elastic regime. The relationship between stress/strain and FCR of the sensor under monotonic loading obeys polynomial formulas. As the sensor is embedded into column, regardless of the concrete strength grade is C30 or C50, the piezoresistive behavior of the embedded sensor undergoes two phases, which is different from that of the sensor before embedded. This difference between the output signal characteristics results from the Poisson's ratio and elastic modulus differences of sensor and concrete. In addition, the presence of sensor does not impact the bearing capacity of concrete column. The developed sensor is therefore suitable to be embedded into prefabricated components to make smart building products which can be calibrated for structural monitoring in real applications.