## 2 Method
### Experimental Protocol  
As mentioned above, the present experimental protocol consists of the realization of several tests for different cement mortars including various amounts of PCM, the idea being to have the same ratio of cement/sand (here 1:2.6) in each mixture. At first, sand (siliceous rounded sand 0.4 mm) and cement (CEM I 52.5 N complying with the EN 196-1 standard) are mixed in order to homogenize components with laboratory moisture content. Secondly, the PCM and water are added at the end of the mixing process in order to expose micro-capsules as short as possible to mechanical stress. The quantity of water added to make the composite mortars does not depend on the quantity of cement but rather on the quantity of PCM included, and it can be very significant due to the high specific surface of the micro-encapsulated PCM. The ratio of PCM estimated in each mixture is calculated using the mass of solid materials, i.e., sand, cement, and PCM. The water added is considered as the required water for the setting of mortar. Practically, to achieve a satisfactory workability, this needed water is dependent on the quantity of micro-capsules. Yet, the real needed water can not be controlled and therefore, free water is present in all samples. When drying, this later one will be replaced by cavities which are consequently different from one sample to another. Concretely, this implies that the dependency of some parameters (the density, the thermal conductivity, and the heat capacity) do not depend only on the PCM amount. Lastly, all associated densities for each material are furnished in Table 1. Three home-made composite mortars were realized in moulds of \(250\times 250\times 40\) mm\({}^{3}\) and all samples have been dried in the laboratory over several months before being used for the experiments. The weight of samples was monitored before and after the tests. No noticeable variations have been seen, since the differences were of the same order as the precision of the scale (0.1 g), which highlights a stable water content during the tests. Thus, the characteristics of the mortars studied are presented in Table 2, where each mortar is named according to its PCM mass percentage. Concretely, the previous compositions can also be given in mass of PCM per unitaire volume: this leads to the values of 175, 241.3, and 272 kgMCP/m\({}^{3}\) for each case, respectively. The micro-encapsulated PCM used here for the home-made mortars is the well-known BASF's Micronal(r) DS 5001 X, where the PCM is contained in the core of micro-capsules ranging from 2 um to 20 um in diameter. Practically, BASF claims that the micro-capsules are completely sealed, safe to process, and free of formaldehyde. It is also specified that the encapsulation process protects the wax in its very pure form, resulting in a high heat storage capacity of 110 kJ kg\({}^{-1}\) being permanently guaranteed. The melting point of Micronal(r) DS 5001 X, given by the manufacturer, is about 26 \({}^{\circ}\)C. We realized the characterization of the PCM included in our composite materials with a pyris Diamond Perkin-Elmer DSC and we concluded that the latent heat is around \(99\pm 10\) kJ kg\({}^{-1}\). This result is detailed within [68]. After the composite mortars have dried and hardened, the samples are placed in the experimental set-up, as depicted in Figure 2. First, the mortar is surrounded by an insulated ring. This ring avoids the heat losses by the lateral sides and enables 1D transfer towards the studied sample in the \begin{table}
\begin{tabular}{l c c c} \hline \hline
**Material** & **Sand** & **Cement** & **Water** & **PCM** \\ \hline \(\rho\) (kg m\({}^{-3}\)) & 1600 & 3060 & 1000 & 300 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Densities for all the involved materials. Figure 1: Graphical abstract of the present method.