## 3 Results and Discussion
### EDS Analysis  
Figures 10-14 illustrate our EDS analyses of the surface of the hardened plain cement paste, the hardened cement pastes blended with TEOS/PVP NFs and CNT-TEOS/PVP NFs, and the local zone containing the nanofibers inside the pastes. In general, the element components in all the pastes are consistent together. The main elements of all three samples  
Figure 8: SEM images of cement matrix containing TEOS/PVP NFs. (**a**) magnification of 20 k, (**b**) magnification of 50 k.  
Figure 9: SEM images of cement matrix containing CNT-TEOS/PVP NFs. (**a**) magnification of 20 k, (**b**) magnification of 50 k.  
are Ca, Si, Al, and O, which are the components of common hydrated products, such as CH, CSH, calcium aluminate hydrates (CAH), etc. [36; 37; 38; 39; 40]. The main reactions of the hydration process are shown in Equations (1)-(3) below:  
\[\mathrm{C_{3}A+6H\to C_{3}AH_{6}} \tag{1}\]  
\[2\mathrm{C_{3}S+6H\to C_{3}S_{2}H_{3}+3 CH} \tag{2}\]  
\[2\mathrm{C_{2}S+4H\to C_{3}S_{2}H_{3}+CH} \tag{3}\]  
However, the proportion of Si element (in SiO\({}_{2}\)) in the plain paste is less than that in the pastes including nanofibers, around 3.57 wt% in the plain paste compared with 4.07 wt% in both pastes blended with TEOS/PVP NFs and CNT-TEOS/PVP NFs (see Figures 10, 11 and 13, and Table 8). Especially in the local zone that contains nanofibers, the proportions of Si element are the highest at around 5.64 wt% and 5.38 wt% in the zone containing TEOS/PVP NFs and CNT-TEOS/PVP NFs, respectively (see Figures 12 and 14, and Table 8). From our results, we observed that the hydration products in all samples are consistent with each other. However, the content of the Si element changed among the three samples. As a result, the more content of the Si element added, the more the CSH component increases. Therefore, the structure becomes more compacted, increasing the material's compressive behavior. Furthermore, a comparison of the ratio between Ca and Si (Ca/Si) can reflect the situation of CSH in cement hydration products. Table 8 shows that the highest Ca/Si ratio belongs to the hardened plain cement paste (4.87), and it reduces in the TEOS/PVP NFs-blended cement paste and the CNT-TEOS/PVP NFs-blended cement paste (3.81 and 2.68, respectively). [PERSON] et al. [41] and [PERSON] et al. [42] concluded that the reduction in the Ca/Si ratio complied with the increase in the silica reactive for the formation of CSH. Therefore, the lowest Ca/Si ratio observed from the EDS analysis of the paste blended with CNT-TEOS/PVP NFs is comparable to the highest previously observed compressive behavior. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Element** & **Wt\%** & **Wt\% Sigma** & **Atomic \%** & **Standard Label** \\ \hline \multirow{8}{*}{Plain paste} & C & 6.70 & 0.41 & 11.69 & C Vit \\  & O & 47.48 & 0.33 & 62.21 & SiO\({}_{2}\) \\  & Mg & 1.90 & 0.05 & 1.64 & MgO \\  & Al & 2.17 & 0.05 & 1.69 & Al\({}_{2}\)O\({}_{3}\) \\  & Si & 4.78 & 0.07 & 3.57 & SiO\({}_{2}\) \\  & S & 0.82 & 0.04 & 0.54 & FeS\({}_{2}\) \\  & K & 1.23 & 0.05 & 0.66 & KBr \\  & Ca & 33.19 & 0.24 & 17.36 & Wollastonite \\  & Fe & 1.73 & 0.11 & 0.65 & Fe \\ \hline \multirow{8}{*}{T28S/C28S} & C & 9.54 & 0.39 & 16.40 & C Vit \\  & O & 45.00 & 0.32 & 58.08 & SiO\({}_{2}\) \\  & Na & 0.92 & 0.05 & 0.83 & Albite \\  & Mg & 0.55 & 0.04 & 0.47 & MgO \\  & Al & 1.60 & 0.05 & 1.22 & Al\({}_{2}\)O\({}_{3}\) \\  & Si & 5.54 & 0.07 & 4.07 & SiO\({}_{2}\) \\  & S & 0.76 & 0.04 & 0.49 & FeS\({}_{2}\) \\  & K & 4.46 & 0.07 & 2.36 & KBr \\  & Ca & 30.14 & 0.22 & 15.53 & Wollastonite \\  & Fe & 1.47 & 0.11 & 0.54 & Fe \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Elemental analysis from EDS results.