Piezoresistive behaviors of self-sensing cementitious composite with well-dispersed carbon nanotube

The well-dispersed carbon nanotubes (CNTs) were developed by a combination of surfactant modification and ultrasonic treatment. The dispersion of CNTs in solution was evaluated using ultraviolet-visible spectrophotometry , zeta potential (ZP), dynamic light scattering and scanning electron microscope (SEM). The well-dispersed CNTs modified self-sensing cementitious composites (CNT-SSCCs) were prepared. The micromorphology of CNT-SSCCs was investigated by SEM and mercury intrusion porosimetry . The influence of CNTs on the polarization effect and conductivity of SSCC was evaluated by the digital acquisition and recording system. The CNT-SSCCs were loaded under different modes by a universal testing machine. The piezoresistive response of CNT-SSCCs was evaluated and the piezoresistive mechanism was discussed. Moreover, the workability and mechanical properties of CNT-SSCCs were evaluated by flow table, compressive and flexural tests. Results show that the particle size of CNTs significantly decreases, with the ZP reaching −48.7 ± 4.3 mV and the absorbance increasing to 2.21 after surfactant modification by sodium dodecyl sulfate and ultrasonic treatment for one hour, indicating the well-dispersed CNTs are obtained through the dispersion processing. The incorporation of well-dispersed CNTs can distribute in the SSCC matrix evenly and improve the pore structure of SSCC. The well-dispersed CNTs at an appropriate content (1.5 %-2 %) can endow the SSCC with well electrical conductivity and superior piezoresistive response under the combined actions of CNT-to-CNT contact, CNT-to-CNT tunneling and pore structure changes. The polarization time of SSCC gradually decreases with the increase of CNT content. The SSCC with 2 % well-dispersed CNTs achieved a maximum stress sensitivity of 1.23 %/MPa with a gauge factor of 169.51. • The well-dispersed carbon nanotubes were developed. • The CNT-SSCCs exhibit excellent conductive and piezoresistive properties. • The conductive and piezoresistive mechanism of CNT-SSCCs were revealed.