## 3 Materials and Methods
### Materials
#### 3.2.1 Artificial Climatic Cycles--FITOCLIMA Chamber Setting  
Specimens were exposed to artificial climatic cycles in an ARALAB FITOCLIMA 500 EC45 climatic chamber (temperature range of \(-\)45-180 \({}^{\circ}\)C, humidity range of 10-90%, and an accuracy of 0.1). The chamber was set up to reproduce four seasons of subpolar climatic conditions. Setting data were obtained from a regional meteorological station (Table 1). Slate specimens were exposed to one series of 30 days for each season following the order described in Table 2 (from winter to fall). Each season included controlled conditions of temperature and rainfall. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Season**} & **Average Min.** & **Average Max.** & **Average Rainfall** \\  & **Temperature (\({}^{\circ}\)C)** & **Temperature (\({}^{\circ}\)C)** & **Accumulation (mm)** \\ \hline Winter & \(-\)12.6 & \(-\)4.2 & 362 \\ Spring & 0.9 & 6.7 & 723 \\ Summer & 5.9 & 13.1 & 581 \\ Autumn & \(-\)7.5 & \(-\)0.5 & 417 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Seasonal climatic data obtained from Livingno meteorological center (Italy) and selected for each season simulation in the climatic chamber ARALAB FITOCLIMA 500 EC45. \begin{table}
\begin{tabular}{l l l l l} \hline \hline  & **Conditioning** & **Step (i)** & **Step (ii)** & **Step (iii)** \\ \hline Winter—repeated for & & 2 h l \(-\)12.6 \({}^{\circ}\)C & 1:30 h l \(-\)12.6 \({}^{\circ}\)C\(\rightarrow\)\(-\)4.2 \({}^{\circ}\)C & 2:30 h l \(-\)4.2 \({}^{\circ}\)C\(\rightarrow\)\(-\)12.6 \({}^{\circ}\)C \\ \hline Spring—repeated for & & 2 h l 0.9 \({}^{\circ}\)C & 1:30 h l 0.9 \({}^{\circ}\)C\(\rightarrow\)\(-\)6.7 \({}^{\circ}\)C & 2:30 h l 6.7 \({}^{\circ}\)C\(\rightarrow\)0.9 \({}^{\circ}\)C \\ \hline Summer—repeated for 1 month & & 2 h l 5.9 \({}^{\circ}\)C & 1:30 h l 5.9 \({}^{\circ}\)C\(\rightarrow\)13.1 \({}^{\circ}\)C & 2:30 h l 13.1 \({}^{\circ}\)C\(\rightarrow\)5.9\({}^{\circ}\)C \\ \hline Fall—repeated for & & 2 h l \(-\)7.5 \({}^{\circ}\)C & 1:30 h l \(-\)7.5 \({}^{\circ}\)C\(\rightarrow\)\(-\)0.5 \({}^{\circ}\)C & 2:30 h l \(-\)0.5 \({}^{\circ}\)C\(\rightarrow\)\(-\)7.5 \({}^{\circ}\)C \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Detailed description of the selected temperatures and steps for each season simulation in the climatic chamber ARALAB FITOCLIMA 500 EC45. Each cycle consisted of 6 h exposure according to Table 2 and Figure 4. Each season simulation was automatically performed and consisted of a cycle repetition for 30 days that combined preliminary soaking and rainfall for 1 h at 10 \({}^{\circ}\)C at the beginning of each cycle. The conditioning step allowed soaking the slate specimens at the beginning of each cycle through the combined action of simulated rainfall and complete immersion of the samples. The criteria to assess the simulated subarctic climate effect on slate were based on the EN 12371 recommended tests, with the addition of other relevant properties: (i) initial and final visual inspection (after the season simulation in the climatic chamber as described in Table 2); (ii) initial and final uniaxial compressive strength and flexural strength under concentrated load, anchor rupture load, point load strength index, P-wave ultrasound speed, Young's modulus, apparent density and open porosity, color, and roughness measurement. In the last 15 min of the conditioning step, the water was drained, the rain stops, and the temperature started decreasing at a rate of approximately 2.8 \({}^{\circ}\)C/min until it reached the initial temperature of each season. The same temperature rate was used after step (iii) at every beginning of a new condition stage. The cycle duration set by this experiment in the climatic chamber (6 h duration) allowed the samples to reach a uniform temperature including the interior, confirmed through continuous temperature monitoring with a mobile temperature sensor placed inside the thicker specimen used (50 mm thickness--prismatic specimens).