Research Article
Cement Pastes and Mortars Containing Nitrogen-Doped and Oxygen-Functionalized Multiwalled Carbon Nanotubes
Figure 6
SEM images of hydrated Portland cement paste at the initial hours of the hydration process. The images in (a), (b), and (c) represent the cement paste based on ordinary Portland cement (OPC) without carbon nanotubes. The images in (d), (e), and (f) display cement paste based on OPC and nitrogen-doped carbon nanotubes (MWCNTs-Nx). The images in (g), (h), and (i) display cement paste based on OPC and MWCNT-Ox (carbon nanotubes with epoxy, hydroxyl, and carbonyl groups on the surface). The images clearly show the time-dependent morphology of the samples. The MWCNT-Nx concentration in all of the samples is 0.1% with respect to the cement mass; a similar concentration is also used for samples with MWCNT-Ox.
| (a) Cement paste without MWCNT |
| (b) Cement paste without MWCNT |
| (c) Cement paste without MWCNT |
| (d) Cement paste with MWCNT-Nx |
| (e) Cement paste with MWCNT-Nx |
| (f) Cement paste with MWCNT-Nx |
| (g) Cement paste with MWCNT-Ox |
| (h) Cement paste with MWCNT-Ox |
| (i) Cement paste with MWCNT-Ox |