## 4 Results and Discussion  
### Uniaxial Compressive Strength of Mortar  
According to the results of the compressive tests, the mortars analyzed in this study are characterized by UCS values ranging from 0.17 MPa to 1.49 MPa. For each specimen, the maximum of the stress-strain curve has been selected and identified as the compressive strength of the material. Such values are summarized in Table 3 and sorted from the smallest to the greatest. The sampling location is also reported to highlight that, except for the 3009-5 sample, the material coming from the masonry face furnished the highest values of UCS. This experimental evidence confirms that the inner part of such a type of masonry wall is the weakest one, made of a material having poorer mechanical properties than the ones of the outer parts. Even though this aspect is crucial in properly evaluating the overall mechanical response of the structural element, its quantification is generally impossible due to the impossibility of directly testing the inner material. In this context, therefore, the available measurements are very rare as well as important. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Site** & **Sample** & **h** & **lmax** & **lmin** & **h/d** \\
**ID** & **Name** & **[cm]** & **[cm]** & **[cm]** & **[-]** \\ \hline
3000 & 3000 & 5.83 & 4.65 & 4 & 1.2 \\ \hline
3004 & 3004 & 6.9 & 6 & 4.9 & 1.13 \\ \hline
3008 & 3008 & 4.8 & 3.6 & 3.4 & 1.22 \\ \hline
3011 & 3011 & 4.7 & 4.5 & 2.6 & 1.22 \\ \hline
3002 & 3002-C & 4.2 & 3.05 & 2.88 & 1.26 \\ \hline
3006 & 3006-2 & 4.4 & 2.55 & 2.2 & 1.65 \\
3006-3 & 3006-3 & 4.55 & 2.25 & 2.2 & 1.81 \\ \hline
3009 & 3009 & 4.86 & 2.85 & 3.35 & 1.07 \\  & 3009-2 & 3.6 & 4.2 & 2.7 & 0.95 \\
3009 & 3009-3 & 3.3 & 3.5 & 3.4 & 0.85 \\  & 3009-4 & 4.3 & 3.1 & 2.3 & 1.43 \\  & 3009-5 & 2.8 & 2.4 & 2.2 & 1.08 \\ \hline
3010 & 3010-A & 4.6 & 2.47 & 2.4 & 1.67 \\  & 3010-B & 4.75 & 2.6 & 2.48 & 1.66 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Geometrical characteristics of the samples. Figure 6: Some of the tested mortar samples. In order to evaluate the possible effect of the specimen geometry on the measured compressive strength, each UCS value was plotted against the corresponding slenderness ratio, as shown in Figure 7. Moreover, this comparison has been done by considering three different classes of mortar, identified based on the UCS values range: Class I (UCS < 0.5 MPa), Class II (0.5 MPa \(\leq\) UCS < 1 MPa), and Class III (UCS \(\geq\) 1 MPa). Even though the number of samples for each class is limited (especially regarding Class II and Class III), no evident dependency of the UCS value from the slenderness has been found, at least within the slenderness ratios considered in the experimental testing. For a given class, it seems that the variability of the compressive strength is more related to the intrinsic inhomogeneity of the material rather than the geometrical features of the samples. As far as Class I is concerned, for instance, it can be observed that the variability of the UCS value for a fixed slenderness ratio is greater than the variability found for different slenderness ratios. Such consideration can be also observed for the samples owing to Class III. Only for the data of Class II, an increase of the compressive strength as the slenderness decreases can be detected. However, based on the findings concerning the other two classes and the very limited number of specimens, such a relationship between the UCS values and the corresponding slenderness ratios seems not to be representative. Naturally, such an aspect requires further study, and the possibility of testing more samples characterized