Influences of multi-walled carbon nanotube (MCNT) fraction, moisture, stress/strain level on the electrical properties of MCNT cement-based composites

Multi-walled carbon nanotube (MCNT) cement-based composites (MNTCCs) with seven different volume additions of MCNT (V) were prepared with surfactant ultrasonic dispersion process. A Wheatstone-based data acquisition technique was developed to simultaneously obtain the electrical resistances, the uniaxial stresses (σc), and the longitudinal strains (εl) of the cured MNTCCs under compressive loading. The percolation threshold, humidity impact on initial resistivity (Ïin), and self-sensing piezoresistivity under mono- and cyclic-loading of the MNTCCs were correspondingly investigated. Results reveal that, the Ïin of MNTCC successively conforms to tunneling transition and percolation effect along with V increment; Fraction change in resistivity (ΔÏ) of MNTCCs with 1.31"‰vol.% MCNT (round percolation threshold) after excluding humidity impact can steadily and linearly alter with σc or εl, and effectively reflect the microstructure changes and crack emerging; The corresponding strain sensitivity, reproducibility of the ΔÏ-εl curve can maintain above 132, less than 5%. These consequences favor the MNTCCs to be intrinsic sensors applied in infrastructure for real-time monitoring of cyclic loadings with high sensitivity, stable and fast responses.