## 2 Materials and Methods
### Selection of Materials  
The materials for the design of lime-cork mortar were selected based on various characteristics, including composition, type class, grain size, aggregate size, natural context, and recycled content; in particular, mechanical properties (compressive strength) and thermophysical properties (thermal conductivity) were also considered. The selection of materials was conducted according to UNI EN 998-1 [27].  
The choice of binder to be used as a matrix base was made by selecting among the products of natural origin available on the market; among these, the only one that met the requirements mentioned in the preamble was the B-Fluid X/A lime. This is a natural hydraulic lime NHL-5, classified according to EN 459-1:2010 [28], produced completely naturally through the firing of calcareous clay [marl] and without any chemical additives; it is composed mainly of calcium silicates, aluminates, and calcium hydroxide. The stone was fired at temperatures between 900 \({}^{\circ}\)C and 1100 \({}^{\circ}\)C. Subsequently, a slow and careful hydration process of the stone was carried out to obtain a final product that leads to better preservation of the environment.  
Table 1 shows the features of the selected commercial product.  
The insulating material used in the designed matrix is granulated cork, a sustainable local product of natural origin. Cork granulate was chosen for its excellent thermal properties compared to commercial products, with a thermal conductivity of 0.043 W/m\({}^{2}\)K and an apparent density of 105 kg/m\({}^{3}\), as detailed in the Table 2.  
The production process of insulating material is shown in Figure 2.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Binder** & **Granulometry (mm)** & **Density (kg/m\({}^{3}\))** & **Compressive Strength (\(\sigma\) (N/mm\({}^{2}\))** & **Thermal Conductivity (W/m\({}^{2}\)K)** \\ \hline Natural hydraulic & from 0 to 4 & 1350.00 & 5.00 & 0.066 \\ Lime NHL 5 & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Features of the selected binder.  
Figure 2: Cork granule production process: (**a**) Forests, natural origin of the cork cycle; (**b**) Cork de-de-barking; (**c**) Maturation of natural cork; (**d**) Boiling cork; (**e**) Grinding of cork into granules; (**f**) Packaging cork granules. Source: [29].  
As seen in detail in Figure 2, the cork oak is born spontaneously in the Mediterranean basin; the cork is obtained from the decortication of the oak trees of Calabria, which can be performed by forestry regulation every 9 years on the same plant after the first harvest, so it must wait up to 25 years from planting.  
The industrial process of cork extraction is simple and has a low environmental impact; in fact, it is divided into several stages, as described in Figure 2. Once the bark has reached the right degree of humidity, it is crushed, separated from woody parts or impurities, and then placed in metal blocks, closed, and heated with steam at about 350-380 \({}^{\circ}\)C. After about 20 min, the result is a block of cork that has become dark due to temperature in a completely natural agglomeration process that uses the suberine and other waxy substances contained in the bark. These substances dissolve under the effect of heat and allow the granules, which have expanded in the meantime, to settle without any other chemical substance being added [30; 31].  
The choice of cork was made because this material has low density, low thermal conductivity, and water resistance, which, when mixed with mortar, can effectively improve the thermal insulation and moisture properties of mortar materials.  
Moreover, the component related to fine aggregates was instead natural river sand from Lake Massaciuccoli, having a rounded particle size of 1.16 mm in diameter, according to UNI EN 1015-1 [32]. Natural sand (bulk density: 1590 kg/m\({}^{3}\)) was selected using a sieve with a size of 0.1-2 mm.