## 2 Materials and Methods
### Experimental Programme
#### 2.3.1 Physical Characterization Tests  
In this section, the following physical characteristics of the composites have been analysed: bulk density, thermal conductivity, capillary water absorption, and total water absorption. These tests are described below.  
The bulk density was determined according to the recommendations of the UNE 102042:2023 standard [44]. For this purpose, the ratio between the mass and volume of each sample was determined, having been previously dried in an oven for 24 h at a temperature of 45 \({}^{\circ}\)C \(\pm\) 1 \({}^{\circ}\)C.  
For the thermal conductivity test, three 24 \(\times\) 24 \(\times\) 2 cm\({}^{3}\) plaster plates of each type of composite were used. The thermal conductivity coefficient was determined using the heat flow meter method (HFM). The test consists of placing the board between two conditioned spaces with a large temperature difference according to the standards [42]. Temperature was set at 60 \({}^{\circ}\)C inside and 18 \({}^{\circ}\)C outside. Once these temperatures are reached, the sample remains at test conditions until it reaches a steady state. At this point, the thermal conductivity coefficient is measured for 30 min, taking two measurements per minute. With these results, the final value is extracted using the median. This test was conducted in the physics laboratory of the Escuela Tecnica Superior de Edificacion de Madrid.  
For the capillary water absorption test, RILEM RC 25-PEM standard [40] indications were followed, positioning the 4 \(\times\) 4 \(\times\) 16 cm\({}^{3}\) samples vertically on a 1 cm-high grid placed in a container. The container is filled with water until it reaches the top of the grid. After five minutes, water height is marked on the sample. From this point on, the height is marked every minute until 15 min. The final height reached shows the greater or lesser absorption of water by capillary action in the composites, reflecting the absorption rate.  
\begin{table}
\begin{tabular}{c c c c} \hline
**Series** & **Dimensions** & **Tests** & **Standard** \\ \hline \multirow{4}{*}{SERIES I} & \multirow{4}{*}{4 \(\times\) 4 \(\times\) 16 cm\({}^{3}\)} & \multicolumn{2}{c}{Shore C Hardness} \\ \cline{3-4}  & & Flexural strength & UNE-EN 13279-2 [31] \\ \cline{3-4}  & & Compressive strength & \\ \hline \multirow{4}{*}{SERIES II} & \multirow{4}{*}{4 \(\times\) 4 \(\times\) 16 cm\({}^{3}\)} & Capillarity water absorption & RILEM RC 25-PEM [40] \\ \cline{3-4}  & & Total water absorption & UNE-EN 520 [41] \\ \hline \multirow{4}{*}{SERIES III} & \multirow{2}{*}{24 \(\times\) 24 \(\times\) 2 cm\({}^{3}\)} & \multirow{2}{*}{Thermal conductivity} & UNE-EN 1946-3 [42] \\ \cline{3-4}  & & UNE-EN 14246 [43] \\ \hline SERIES IV & \multirow{2}{*}{30 \(\times\) 40 \(\times\) 1.5 cm\({}^{3}\)} & Plates pure bending test & UNE-EN 14246 [43] \\ \hline \end{tabular}
\end{table}
Table 4: Summary table with samples produced and list of tests and standards.  
Finally, the total water absorption coefficient is conducted according to UNE-EN 520 standard [41]. For this test, samples must be completely immersed in a container with water for a minimum period of two hours. Once this has been done, they are weighed repeatedly to obtain the total amount of water absorbed until the difference between two consecutive measurements is less than 0.1 g. Total water absorption percentage is determined by the following expression:  
\[\text{Total Absorption}=\frac{mf-m0}{m0}\times 100 \tag{1}\]  
where \(m0\) is the initial mass of the dried sample in grams and \(mf\) is the final mass of the sample after immersion in water.