## 4 Experimental Program  
### Materials Used  
Ten samples with dimensions of 4 \(\times\) 4 \(\times\) 16 cm (\(\pm\)0.2 cm), made of different building materials, were performed; steel (S), aerated concrete (AC), sand-line brick (SLB), ceramic brick (CB), fireclay brick (FB), and four concretes: with gravel aggregate and Portland cement (CGA-PC), with gravel aggregate and alumina cement (CGA-AC), with ceramic aggregate and Portland cement (CCA-PC), with ceramic aggregate and alumina cement (CCA-AC), and granite (G). The samples were prepared in the majority by excision of the building elements (blocks, bricks, cobblestones). Concrete samples were molded in steel molds.  
The steel sample was cut from a full bar with dimensions of 40 \(\times\) 40 \(\times\) 12,000 mm. The quality of the steel, designated according to EN 10025-2:2004, was defined as S 355 J2.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Material**} & **Heat Capacity** & **Initial** & **Maximum** & **Temperature** & **Heat** \\  & & **(M/(m\({}^{3}\)-K))** & **Temperature** & **Temperature** & **Difference** & **Accumulation** \\  & & & **(M/(m\({}^{3}\)-K))** & **(\({}^{\circ}\)C)** & **(\({}^{\circ}\)C)** & **(\({}^{\circ}\)C)** & **Capacity (M/m\({}^{3}\))** \\ \hline
1 & Water & 4.181 & 20 & 100 & 80 & 334.5 \\
2 & Steel & 3.535 & 20 & 1600 & 1580 & 5586.7 \\
3 & Styrofoam & 0.024 & 20 & 80 & 60 & 1.4 \\
4 & Granite & 1.789 & 20 & 900 & 880 & 1574.2 \\
5 & Common brick & 1.190 & 20 & 380 & 360 & 428.4 \\
6 & Fireclay brick & 1.190 & 20 & 1400 & 1380 & 1642.2 \\
7 & Ordinary concrete & 2.769 & 20 & 250 & 230 & 636.7 \\
8 & Heat-resistant concrete & 2.769 & 20 & 1000 & 980 & 3266.8 \\ \hline \hline \end{tabular}
\end{table}
Table 2: The maximum amount of the thermal energy, which can be stored in a unit volume of the material.  
The sample of aerated concrete was cut using a saw with a diamond disc, from a block with dimensions of 240 \(\times\) 240 \(\times\) 590 mm. The density of the block was 700 kg/m\({}^{3}\), compressive strength was 4 MPa, thermal conductivity was 0.7 W/(m\({}^{2}\cdot\)K), and the open porosity was 28.1%.  
The sand-line brick sample was cut from the product--a brick with dimensions 250 \(\times\) 120 \(\times\) 65 mm. Its density was equal to 1800 kg/m\({}^{3}\), its thermal conductivity was 0.8 W/(m\({}^{2}\cdot\)K), and its open porosity was 15.4%.  
The sample of ceramic brick was obtained from a solid brick of dimensions 250 \(\times\) 120 \(\times\) 65 mm. The material's water absorption is no higher than 16%, its compressive strength was 15 MPa, its frost resistance was as for bricks of the 10 MPa class, and its open porosity was 16.9%.  
The fireclay brick sample was cut from a full brick. The material has a minimum compressive strength of 30 MPa, an operational temperature of 1370 \({}^{\circ}\)C, an open porosity of 20%, and an apparent density of 2.1 g/cm\({}^{3}\).  
The granite rock sample was obtained from a rock block. A diamond disc was used for its preparation. The material has a specific density of 2.8 g/cm\({}^{3}\), a bulk density of 2.7 g/cm\({}^{3}\), a compressive strength of 59 MPa, a modulus of elasticity of 360 GPa, water absorption of 0.8%, and open porosity of 2.2%.  
The concretes' compositions used in the tests, as well as their basic properties, are described in the Section 4.3.