Optimization of preparation parameters and testing verification of carbon nanotube suspensions used in concrete

Carbon nanotubes (CNTs) have received extensive attention due to their exceptional properties and wide range of applications. However, the agglomeration of CNTs in aqueous solutions and organic solvents significantly limits their large-scale application. In this study, the microscopic morphology and dispersion stability of the CNT suspensions were analyzed, and the most suitable surfactant in this study was selected. The preparation parameters of the CNT suspensions were optimized, and uniaxial compression tests were conducted on carbon nanotube concrete (CNTC) prepared using the optimized parameters. Scanning electron microscope analysis was used to investigate the improvement in the microstructure of the concrete by CNTs. Transmission electron microscope micrographs of the polyvinyl pyrrolidone (PVP)-CNT suspensions exhibited a uniformly distributed CNT cross-linked network. The absorbance reduction ratio of PVP-CNT suspensions after standing for 90 days was 13.75 and 22.41%, respectively. The absorbance reduction ratio of the suspensions first increased and then decreased with increasing dispersant ratio and ultrasonic dispersion time and increased with increasing ultrasonic power ratio. Compared with that of plain concrete, the uniaxial compressive strength of CNTC significantly improved, with a maximum increase of 18.15% when the content was 0.10%, and the failure mode exhibited typical shear failure characteristics. The optimized preparation parameters for the CNT suspensions were a PVP-to-multiwalled carbon nanotube mass ratio of 4:1, an ultrasonic dispersion time of 20 min, and an ultrasonic power of 60%. These optimized parameters are ideal choices for preparing CNT cement-based composite suspensions.