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

Abstract

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.