Stress-sensitivity of carbon nanotube-grafted-carbon fiber incorporated cement-based composites

The article studied the stress-sensitivity of carbon nanotube-grafted-carbon fiber incorporated cement-based composites under temperature and humidity, and further investigated the piezoresistive stability of the composite embedded in the concrete as a sensor. This study employed hydrothermal synthesis to graft carbon nanotubes (CNTs) onto the surface of carbon fibers (CFs) to prepare CNT-grafted-CF reinforced composites (CNT-CF). CNT-CF was added to cement to prepare CNT-CF incorporated cement-based composites (CNT-CF/CC). The connection of the conductive network and the micromorphology of CNT-CF in the cement matrix were characterized by scanning electron microscope (SEM). Four-electrode method was used to investigate the electrical conductivity. Cyclic loading test was performed to test the intelligent performance of CNT-CF/CC under different temperatures and humidity. The results demonstrated that compared with CFs, CNT-CF was surrounded by more hydration products. The CNTs on the surface of CFs increased the roughness of CFs. SEM images revealed that CNT-CF was more firmly bonded with the cement matrix. Moreover, CNT-CF/CC had better electrical and sensitive properties. Thus, it was explored for the application in stress-sensors for monitoring the change of stress in concrete. The results showed that smart concrete prepared by embedded stress-sensors also exhibited sensitive piezoresistive effect.