Porosity and pore size distribution measurement of cement/carbon nanofiber composites by 1H low field nuclear magnetic resonance

The dispersion effect of carbon nanofibers (CNFs) in aqueous solution and the mechanical properties, porosity, pore size distribution and microstructure of CNFs reinforced cement-based composites were investigated in this paper. To achieve effective dispersion of CNFs, a method utilizing ultrasonic processing and a commercially surfactant were employed. CNFs were incorporated to cementitious materials with the addition of 0.1 wt% and 0.2 wt% of cement with a water/cement ratio of 0.35. The mechanical properties of CNFs/cement composites were analyzed, the porosity and pore size distribution were characterized by H-1 low field nuclear magnetic resonance (NMR), and the microstructure was observed by scanning electron microscopy (SEM). The results indicate that the optimum concentration ratio of MC to CNFs is 2:1 for dispersing in aqueous solution. Moreover, in the field of mechanical properties, CNFs can improve the flexural strength and compressive strength. The increased mechanical properties and the decreased porosity of the matrices correspond to the increasing CNFs content and CNFs act as bridges and networks across cracks and voids.