# Preliminary Study of New Sustainable, Alkali-Activated
## 3 Results
### AAC Characterization  
#### 3.2.1 AAC Physico-Chemical Characterization  
The XRD patterns of CSP and AAC, formulated as a function of the NaOH concentration and L/S ratio, are shown in Figure 4. It should be noted that no significant differences were found between the XRD patterns of both S/L (0.5 and 0.6) ratios. All the diffractograms showed an important halo (between the 2\(\theta\) range from 15\({}^{\circ}\) and 35\({}^{\circ}\)) corresponding to the amorphous phases (vitreous phases) of the CSP, as well as the presence of quartz (PDF-01-085-0457, most important peaks for the identification of this crystalline phase at 26.625\({}^{\circ}\) and 20.827\({}^{\circ}\)) and mullite (PDF-01-079-1457, most important peak for the identification of this crystalline phase at 16.441\({}^{\circ}\)) as the main crystalline phases. The sodium carbonate (PDF-01-072-0628, mainly because of the peaks at 37.985\({}^{\circ}\) and 30.149\({}^{\circ}\)) in small amounts were detected in 4 M formulations (05 LS4M and 06 LS4M), and in higher amounts were also detected for the 8 M formulations (05 LS8M and 06 LS8M). In addition, calcium silicate hydrate (PDF-01-074-1995) was detected for 4 M formulations and potentially  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Compounds** & **CSP (wt \%)** \\ \hline SiO\({}_{2}\) & 70.78 \\ Na\({}_{2}\)O & 11.15 \\ CaO & 9.37 \\ Al\({}_{2}\)O\({}_{3}\) & 4.81 \\ MgO & 1.61 \\ K\({}_{2}\)O & 0.94 \\ Fe\({}_{2}\)O\({}_{3}\) & 0.57 \\ TiO\({}_{2}\) & 0.13 \\ P\({}_{2}\)O\({}_{5}\) & 0.04 \\ MnO & 0.02 \\ LOI & 0.99 \\ \hline \hline \end{tabular}
\end{table}
Table 2: X-ray fluorescence (XRF) results from the CSP raw material.  
Figure 3: Particle size distribution of the CSP after milling used as raw material.  
presented in 8M formulations. Considering the clearest presence of sodium carbonate in 8 M formulations and the evidence of calcium silicate hydrate in 4 M formulations, it can be assumed that the higher the NaOH concentration, the higher the amount of sodium carbonate, and the lower the presence of calcium silicate hydrate. The presence of calcium silicate hydrate is related to CSH gel, which is better determined in 4 M formulations by the peak at 31.650\({}^{\circ}\), probably due to a lower presence of sodium carbonate. Notice that the higher the alkali concentration, the higher the displacement of amorphous halo, due to the formation of NASH gel [33].  
Regarding FTIR characterization, Figure 5 shows the variation of some IR bands depending on the different NaOH formulations, as well as the different L/S ratios. Again, for the same NaOH concentration, it should be noted that no significant differences were found between the FTIR spectra of both L/S (0.5 and 0.6) ratios. A displacement to lower frequencies in the peak around 1000 cm\({}^{-1}\) can be seen from CSP concerning the different AAC formulations, because of the formation of NASH gel [36; 37]. These displacements indicate that the vitreous component was reacting with the NaOH, and therefore, new products of the reaction were formed [38]. As can be seen in the zoomed-in areas of Figure 6, the formulations of 4 M NaOH concentration present slightly lower frequencies than the 8 M NaOH concentration formulations. In addition, three main peaks in both spectra can be observed: (i) a peak at 1400 cm\({}^{-1}\), due to the stretching vibration of CO\({}_{3}\)\({}^{2-}\), in 1 M, 4 M, and 8 M formulations; (ii) a peak between 1020 cm\({}^{-1}\) and 970 cm\({}^{-1}\), because of the asymmetrical stretching peak of Si-O-Si and Si-O-Al in CSP raw material and AAC formulated with 1 M, 4 M, and 8 M NaOH; (iii) a peak at 885 cm\({}^{-1}\), which corresponds to the CO\({}_{3}\)\({}^{2-}\) bending vibration in AAC with 1 M, 4 M, and 8 M NaOH.  
Figure 4: X-ray diffraction (XRD) results for the CSP precursor and the different AAC formulations obtained depending on the liquid-to-solid ratio (L/S) ratios (0.5 and 0.6) and the NaOH concentration.