Introducing carbon nanotubes into concrete: a porosity-based characterization of dispersion

Carbon nanotubes (CNTs) possess the significant ability to improve the properties and performances of cement-based materials, particularly when incorporated with a uniform dispersion. However, the effective characterization of the dispersibility of CNTs in the hardened cement-based materials remains a difficult task. In this study, a porosity-based approach was proposed to evaluate the dispersion of multi-walled carbon nanotubes (MWCNTs) in concrete based on backscattered electron imaging, in which the agglomerated MWCNTs are identified as pores. Moreover, the concept of agglomeration coefficient was introduced to quantify the extent of MWCNTs agglomeration in concrete. The content of carbon element was analyzed in concrete through energy-dispersive X-ray spectroscopy (EDS) to validate the proposed approach. Subsequently, compressive strength, water absorption, and freeze-thaw resistance of MWCNTs-modified concrete were investigated to further verify the effectiveness of the proposed method. At last, mercury intrusion porosimetry, X-ray diffraction and EDS were conducted to elucidated the underlying mechanism of the uniform dispersion of MWCNTs on the improvement of the performance of concrete.