# Characterization and Reactivity of Natural Pozzolans from Guatema
## 3 Results and Discussion
### Properties of Mortars: PC/VP Systems' Workability and Compressive Strength  
Replacing PC with pozzolan reduces workability, which is due to the pozzolan particles' irregular shape. The results of workability with a water/binder of 0.47 are shown in Figure 11 (see Table 1). As shown in Figure 11, replacing cement with VP reduced mortar workability. This behavior is consistent with that in the consulted literature, which reported that the angular shapes of the natural pozzolas' particles caused loss of workability. The compressive strength results for each prepared mortar at curing times of 28, 90, and 180 days for 15%, 25%, and 35% cement replacements are presented in Table 8. In any case, the mortars containing pozzolan never exceeded the strengths of the control mortars. In order to determine the contribution of the natural pozzolans to strength development because of pozzolanic activity, the percentage of strength gain (\(SG\%\))\({}_{\%}\) was calculated [34]. This parameter is defined by Equation (7):  
\[SG_{\%\text{C}}=\frac{[R_{c}s-(R_{c}c*S_{\%})]}{R_{c}c*S_{\%}}*100 \tag{7}\]  
where  
Figure 11: Workability of the control mortar and pozzolan-containing mortars (25% replacement) for a water/binder ratio of 0.47. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{2}{c}{**(\%)**} & \multirow{2}{*}{**Mortar**} & \multicolumn{4}{c}{**Compressive Strength (MPa)**} \\ \cline{2-5} \multicolumn{1}{c}{**Replacement**} & & \multicolumn{1}{c}{**28 Days**} & \multicolumn{1}{c}{**90 Days**} & \multicolumn{1}{c}{**180 Days**} \\ \hline
0\% & Control & 45.86 \(\pm\) 1.33 & 55.28 \(\pm\) 0.40 & 59.57 \(\pm\) 2.49 \\
15\% & T & 39.81 \(\pm\) 1.52 & 48.50 \(\pm\) 1.59 & 55.01 \(\pm\) 0.62 \\
15\% & R & 40.99 \(\pm\) 0.67 & 49.34 \(\pm\) 1.36 & 55.43 \(\pm\) 0.98 \\
25\% & T & 36.94 \(\pm\) 0.59 & 47.58 \(\pm\) 1.50 & 53.21 \(\pm\) 1.00 \\
25\% & R & 36.10 \(\pm\) 1.00 & 46.82 \(\pm\) 1.13 & 52.68 \(\pm\) 2.80 \\
35\% & T & 31.77 \(\pm\) 1.49 & 41.19 \(\pm\) 0.70 & 45.98 \(\pm\) 1.95 \\
35\% & R & 32.85 \(\pm\) 0.58 & 40.62 \(\pm\) 0.44 & 47.35 \(\pm\) 0.76 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Compression test results of the samples with a water/binder ratio of 0.47 at 28, 90, and 180 days of curing. \(R_{c}\)s is the compressive strength of the mortar with pozzolan replacement;  
\(R_{c}\)c is the compressive strength of the control mortar;  
\(S_{\%_{c}}\) is the proportion of cement in the mortar with substitution (expressed per unit; e.g., for the mortar with the 25% replacement, \(S_{\%}\) = 0.75). As can be seen in Table 9, there was a slight strength gain in the early curing days, particularly for the highest replacement percentage (35%). The higher the number of curing days, the higher the strength gained in all of the substitutions. Therefore, it can be concluded that further strength gains were obtained with longer curing times and greater strength gains occurred at higher replacement percentages. [PERSON] et al. [35] studied mixtures by replacing cement with VP at a percentage of 45%. The authors concluded that, at early curing times, decreases in the compressive strength values were much more pronounced. The low-medium pozzolanic reactivity of this type of material can, therefore, be confirmed. The new studied doses for the mortars with different water/binder ratios are shown in Table 2. The w/b ratios of 0.53, 0.50, 0.44, and 0.41 were studied, together with the data from the previous section corresponding to the w/b ratio of 0.47, completing the study. In this case, the behavior of the two pozzolans systems with the 25% PC replacement was analyzed, and their behavior was compared with that of the corresponding mixtures using LF as an inert addition. A workability analysis was performed, as shown in Figure 12. The same pattern of reduced workability in all the cement replacements with substitutions for VP was observed for the control mortar values, unlike the mortars with filler substitutions, whose workability increased in relation to the control mortars.