Reinforcing cement with pristine and functionalized carbon nanotubes: experimental and simulation studies

In recent years, the addition of carbon nanotubes to construction materials has attracted considerable interest, due to the improvement of mechanical, electrical, and thermal properties of cement. The incorporation of carbon nanotubes into a cement matrix causes an increase of several mechanical properties of up to 170% even with low carbon nanotubes concentrations. The objective of this study is to analyze the influence of the type of functionalization and number of walls of carbon nanotubes on the interaction between these nanostructures and a cement surface and thus, on the improvement of their mechanical properties. Thus, single-walled and double-walled carbon nanotubes were used to investigate the influence of the number of walls. The effect of carbon nanotube functionalization was studied using carbon nanotubes functionalized with carboxyl and carboxylate groups. The experimental results demonstrate that the incorporation of carbon nanotubes into the cement matrix improves the mechanical properties of the resulting material. Functionalized carbon nanotubes perform better than pristine carbon nanotubes. Electrostatic attractions play a central role in establishing strong interactions between the carbon nanotubes and the cement surface. The presence of neutral polar groups on the carbon nanotube surface also improves this interaction. The number of walls seems to be less important.