# Characterization and Reactivity of Natural Pozzolans from Guatema
## 3 Results and Discussion  
### Physico-Chemical Characterization of Volcanic Pozzolans (VPs)  
The first part of the results obtained in this research work focuses on the complete characterization of the starting materials. The mean particle diameters and parameters of the particle size distribution for the pozzolanic materials are summarized in Table 3. The diameters of the two pozzolans were similar and came very close to the value for PC (20.58 \(\upmu\)m), although they were slightly higher. The granulometric curves for the two VP samples are presented in Figure 1. Both were similar and presented a unimodal aspect. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Cement** & **Type of** & **Pozzolan** & **Water** & **Sand** \\  & **(g)** & **Pozzolan** & **(g)** & **(g)** & **(g)** \\ \hline CEM II & 450.0 & - & - & 211.5 & 1350 \\ CEM II + 15\%T & 382.5 & T & 67.5 & 211.5 & 1350 \\ CEM II + 15\%R & 382.5 & R & 67.5 & 211.5 & 1350 \\ CEM II + 25\%T & 337.5 & T & 112.5 & 211.5 & 1350 \\ CEM II + 25\%R & 337.5 & R & 112.5 & 211.5 & 1350 \\ CEM II + 35\%T & 292.5 & T & 157.5 & 211.5 & 1350 \\ CEM II + 35\%R & 292.5 & R & 157.5 & 211.5 & 1350 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Mortar doses for the mixtures with different pozzolan percentages. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Cement** & **Type of** & **Admixture** & **Water** & **Sand** \\  & **(g)** & **Admixture** & **(g)** & **(g)** & **(g)** \\ \hline  & 450.0 & - & - & 238.5 & 1350 \\  & 450.0 & - & - & 225.0 & 1350 \\ CEM II & 450.0 & - & - & 211.5 & 1350 \\  & 450.0 & - & - & 198.0 & 1350 \\  & 450.0 & - & - & 184.5 & 1350 \\ \hline  & 337.5 & T, R, or LF & 112.5 & 238.5 & 1350 \\  & 337.5 & T, R, or LF & 112.5 & 225.0 & 1350 \\ CEM II + 25\%X & 337.5 & T, R, or LF & 112.5 & 211.5 & 1350 \\  & 337.5 & T, R, or LF & 112.5 & 198.0 & 1350 \\  & 337.5 & T, R, or LF & 112.5 & 184.5 & 1350 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mortar doses for the mortars with different w/b ratios. X-ray fluorescence (XRF) was used to determine the chemical composition of natural pozzolans T and R. The contents of oxides are shown in Table 4; the table shows that the two samples had a high silica (SiO\({}_{2}\)) content (T = 70.49% and R = 72.06%). This is a decisive oxide for classifying something like pozzolanic material. In addition, a significant alumina (Al\({}_{2}\)O\({}_{3}\)) percentage (T = 13.57% and R = 12.67%) appeared. The contents of calcium and iron oxides were very low. The cement composition is included in the same table because it was the material that was also used to manufacture the pastes and mortars. The sums of the three acid oxides (SiO\({}_{2}\) + Al\({}_{2}\)O\({}_{3}\) + Fe\({}_{2}\)O\({}_{3}\)) for the T and R pozzolanic reactivity evaluations were 85.89% and 85.87%, respectively. These values represented an oxide content that was potentially reactive and above 75%. This composition fell within the normal ranges published in the bibliography; for example, the quantity of SiO\({}_{2}\) in this type of natural pozzolan varies between 40-70% [28]. The loss on ignition (LOI*) was less than 5%, which fell within the acceptable values for pozzolanic materials. However, the insoluble residue (IR) was slightly over 40%, indicating that a very large part of the material was crystalline and insoluble in both acid and alkaline media. Specifically, the values obtained from the IR were 40.8% and 42.25% for T and R, respectively. This could severely limit their pozzolanic reactivity. In Figure 2, the TGA and DTG curves of the VP samples are plotted. On the TGA curves, continuous loss of mass can be observed within the 250-700 \({}^{\circ}\)C range. The presence of carbonates was not detected in both samples. Some minor losses were associated with