## 2 Materials and Methods
### Materials Characterization  
In addition to the properties of the materials provided by the suppliers, a series of laboratory tests were conducted for a more extensive and detailed characterization for the purposes of this experiment. These tests involved performing a particle size analysis according to the UNE-EN 933-1:2012 standard [47]. Thus, the particle size distribution curves of the different materials were obtained (see Table 2). The values of the thermal conductivity of the materials were determined by means of a TCI analyzer from C-Therm(r), which is a non-destructive test based on the MTPS technique as specified in the UNE-EN ISO 22007-2:2023 [48] and ASTM D7984:21 standards [49]. This technique employs a reflective sensor that applies a constant and instantaneous heat source on the test specimen. The equipment allows for direct measurements of thermal conductivity and thermal effusivity of powders, liquids, gels, and solid materials, the latter ones being the targeted material for this research. To perform the tests, a standard weight is placed on the samples to ensure contact with the sensor. Furthermore, in the tests with solids (such as the limestone aggregate in this study), a contact paste (Wakefield thermal \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Section**} & **Sieve** & **40** & **31.5** & **22.4** & **16** & **11.2** & **8** & **5.6** & **4** & **2** & **1** & **0.5** & **0.25** & **0.063** \\ \hline
**CDW** & \% pass & 100.0 & 95.0 & 62.0 & 60.0 & 50.0 & 40.0 & 36.0 & 30.0 & 20.0 & 16.0 & 15.0 & 10.0 & 5.0 \\ \hline
**Vegetable land** & \%pass & 100.0 & 100.0 & 100.0 & 100.0 & 89.0 & 78.0 & 71.0 & 56.0 & 44.0 & 35.0 & 21.0 & 3.0 \\ \hline
**Expanded clay** & \%pass & 100.0 & 100.0 & 100.0 & 100.0 & 95.0 & 59.0 & 25.0 & 1.9 & 1.0 & 0.0 & 0.0 & 0.0 & 0.0 \\ \hline
**Limestone aggregates** & \%pass & 100.0 & 94.0 & 77.5 & 69.8 & 64.0 & 51.5 & 41.9 & 35.5 & 23.5 & 17.2 & 14.0 & 10.0 & 4.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Particle size distribution of the materials. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Section**} & **Thickness** & **Green Swale – Type 1** & **Green Swale – Type 2** & **Green Swale – Type 3** \\ \hline
**Top layer** & 100 & Vegetable land & Vegetable land & Vegetable land \\ \hline
**Intermediate layer** & 150 & Limestone aggregates & Limestone aggregates & CDW \\ \hline
**Sub-base** & 200 & Limestone aggregates & Expanded clay & Expanded clay \\ \hline
**Lower layer** & 52 & Infiltration Cells & Infiltration Cells & Infiltration Cells \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Materials of the different green swales’ sections. joint compound type 120 silicone) was used to eliminate gaps between the sensor and the sample. Three samples of each material (limestone aggregate, topsoil, recycled aggregates, and expanded clay) were taken in order to perform the tests. The expanded clay was crushed to form a homogeneous powder, as was the topsoil. In the case of the limestone and recycled aggregates, three samples were taken and used to create three stone slabs with two flat sides (see Figure 2). The tests were performed under two different scenarios:  
* Ambient conditions, with the materials tested under laboratory-controlled temperature and relative humidity (RH): T = 18.5 \(\pm\) 0.5 \({}^{\circ}\)C and RH = 80%. * Wet conditions, where the materials were tested under saturated conditions. In the case of the expanded clay and topsoil layers, water was added gradually until a soft consistent paste was formed. For the limestone aggregate specimens, they were immersed in a container with water at a constant temperature of 22.4 \(\pm\) 0.5 \({}^{\circ}\)C for 168.0 \(\pm\) 0.5 h until they reached full saturation. The tests were carried out with constant mass specimens, following the standard procedure depicted in UNE-EN 1097-6: 2014 [50] in all scenarios.