Intelligent monitoring method for axial compression response of concrete short columns using embedded CNTs-modified cementitious sensors

Self-sensing cementitious materials, as a new type of structural-functional integrated material, are ideal monitoring materials for structural health monitoring. This study proposes an intelligent monitoring method for axial compression response of concrete short columns using embedded carbon nanotubes (CNTs)-modified cementitious sensors. The CNTs-modified cementitious sensors were prepared and embedded in concrete short columns with different strength grades. The influence of the sensor embedding on the mechanical properties of the concrete short columns was analyzed to calibrate the sensors. The effects of loading rate, loading method and inclination angle on the compressive sensitivity of the sensors were discussed. Finally, a predictive stress-strain constitutive model of concrete column based on the fractional change in resistivity (FCR) of the sensor was proposed, and the reliability was further verified by comparison with experimental results. The results show that the FCR of sensor embedded in the tested C30, C40, and C50 concrete columns is highly consistent with the calibrated values, showing excellent compatibility with concrete. The sensor can accurately monitor the stress and strain of concrete columns under cyclic loading and constant loading, demonstrating excellent compressive sensitivity, repeatability and stability. The inclination angle significantly influences the sensitivity and stability of sensors embedded in concrete columns, and 20° is the critical inclination angle for the sensor. A stress-strain constitutive model for concrete columns based on the CNTs-modified cementitious sensor was established. The prediction error for the ultimate compressive strength was less than 5%, verifying the reliability of the constitutive model, achieving the self-monitoring of the mechanical response of concrete columns.