## 3 Results and Discussion
### Mortars
#### 3.1.3 Compressive Strength Tests  
With reference to the results of the compression tests, it is observed that the maximum achieved value, 65.38 MPa, results from specimen M6, made with graded sand, slightly higher than the strength of the reference mortar M1 (61.82 MPa). This can be justified by the presence, in sample M6, of sand with a larger particle size (2-4 mm and 4-6 mm) compared to normal mortar (fine grains of 2 mm). The lowest compressive strength value (12.86 MPa) results from specimen M4, containing only expanded polystyrene: the presence of this material as an aggregate, in fact, causes a reduction, due to its hypothesized particle sizes and high porosity, in the mechanical performance of the mortars in which it is incorporated. This is further confirmed for specimens M5, M7, and M8, where the different combination of aggregates, sand, and EPS, provides better mechanical strength values compared to specimens M2, M3, and M4, containing only expanded polystyrene (Figure 12). The one-way ANOVA tests were performed for each tested mix on each investigated property. The results, consistent across all tests, led to rejecting the null hypothesis H0, which posits that the means are different due to natural statistical fluctuation rather than actual differences. Therefore, the tests confirm the initial hypothesis that variations in the mixture composition result in variations in the measured properties. The results of the ANOVA for some of the investigated properties are reported (Tables 9 and 10). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Source of Variation** & **SS 1** & **Df 1** & **MS 1** & **F** & \(p\)**-Value** & **F Crit** \\ \hline Between groups & 0.20505 & 7 & 0.029293 & 29.38468428 & 5.53907 \(\times\) 10\({}^{-8}\) & 2.657197 \\ \hline Within groups & 0.01595 & 16 & 0.000997 & & \\ \hline Total & 0.221 & 23 & & & \\ \hline \hline \end{tabular} \({}^{1}\) SS = sum of squares; Df = degree of freedom; MS = mean square.  
\end{table} 
Table 9: Mortars. ANOVA test for thermal conductivity. Figure 12: Mortar. Results of compressive strength tests on mortars. As for the formulation of mortars, the experimental results reveal that all specimens exhibit a much more fluid behavior compared to the reference sample due to the absence of fine fraction (\(\mathcal{O}<1\) mm), which contributes to aggregative phenomena. From the compression tests, it was observed that the highest values of mechanical strength were obtained from the reference sample and the sample with only sand, while conglomerates based on only polystyrene, a porous material, proved to be the most fragile. A compromise can be achieved in the case of mortars where both lightweight and traditional aggregates are present, with results not too different from standardized mortar. The trend of thermal tests aligns with what was obtained from the perspective of mechanical strengths, meaning that the sample with the highest thermal conductivity is the reference specimen, while the lowest values were obtained in the case of complete sand replacement with EPS. Intermediate values were obtained with mixed aggregates, where the contribution of sand is observed for mechanical strengths, while the lightweight and thermal insulation properties are due to polystyrene. A particular result is the high insulation performance provided by sample M6 (containing only sand) compared to the reference, considering that its strengths are also higher. This result is due to a decrease in density, with a consequent increase in internal porosity, which is compensated by the presence of aggregates with larger dimensions than normal mortar. Based on the compression strength values, a comparison was made with the classification of masonry mortars according to UNI EN 998-2:2016 [74], as outlined in Figure 13. The graph shows that all designed mortars, even those with no sand content, can be used as masonry mortars, falling within the various classes identified by the regulations.