## 3 Results and Discussion
### Study of the Influence of Bentonite Clay on the Properties of Products  
Cylinder samples based on loam and bentonite clay, after drying, were burned in a muffle furnace at 1100 and 1150 \({}^{\circ}\)C for 1 h.  
Table 4 shows the compositions and results of the properties of the samples after burning at 1100 \({}^{\circ}\)C based on loam without additives and the addition of bentonite. The addition of of 10, 15, and 20% bentonite led to a slight decrease in the average density of the samples of 3.5%, 4.7%, and 3.2%, respectively. With the addition of 10 and 15% bentonite, the compressive strength of the products increased by 22.7% and 22.9% corresponding to a compressive strength of 21.42 and 21.46 MPa (grade M 200), respectively. Some research has also shown that the addition of 15 and 20% bentonite to the blast-furnace slag contributes to the production of grade M 175 and M 200 ceramic bricks [2], and the addition of phosphate slag produced wall bricks with a compressive strength of 17.2 to 21.5 MPa or grade M 175 and M 200 [3]. This is probably due to the fact that bentonite is a fusible clay that can easily enter, during burning, solid-phase reactions with loam, blast-furnace, and phosphorus slag to form easily fusible eutectics. This leads to the formation of the melt, which improves the sinterability of the ceramic tiles and, consequently, increases the strength, due to the formation of a glass phase, after the cooling of samples. Samples with 35, 40, 45, and 50% bentonite showed significant transverse cracks after burning. As the amount of bentonite in the samples increased, the size of the cracks became larger. Figure 4 shows photos of the samples with 35 and 40%, bentonite which show significant transverse and longitudinal cracks. In [8], the authors indicated that the addition of bentonite improves the swelling of the clay and this was the basis for the development of lightweight aggregate technology. Apparently, in our studies, the addition of 30% bentonite or more also contributes to the swelling of the ceramic weight, which was manifested in the formation of longitudinal and transverse cracks in the samples. Bentonite contains up to 70% of the mineral montmorillonite (Al\({}_{2}\)(OH)\({}_{2}\))[Si\({}_{4}\)O\({}_{10}\)]\(\cdot\)nH\({}_{2}\)O), and the particle size of the mineral is less than 1 mcm. Monmorillonite swells when moistened and its volume increases 16-fold. The laminar structure of the mineral montmorillonite contains silicate layers, the maximum length between which is about 1.4 nm, that are separated by layers of water molecules, and the thickness of these layers can vary over a wide range. Therefore, drying removes physically and, during burning, chemically bound water, which, in the form of vapor, moves the laminar silicate layers vertically, which leads to the formation of transverse cracks. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & **Compositions** & \multirow{2}{*}{\(\rho_{av.}\)**kg/m\({}^{3}\)**} & **Compressive** & **Full (Total) Volumetric** & \multirow{2}{*}{**Note**} \\  & & & **Strength, MPa** & **Shrinkage, \%** & \\  & & & **Burning Temperature 1100 \({}^{\circ}\)C** & & \\ \hline
**1** & Loam-100\% & 1647 & 17.46 & 4.1 & Color of the sample is \\
2 & Loam-90\%; bentonite-10\% & 1588 & 21.42 & 4.0 & light yellow \\
3 & Loam-85\%; bentonite-15\% & 1570 & 21.46 & 3.8 & Color of the sample is light \\
4 & Loam-80\%; bentonite-20\% & 1594 & 15.58 & 3.4 & yellow with a green tint \\
5 & Loam-75\%; bentonite-25\% & 1604 & 11.97 & 2.9 & There is small transverse \\  & Loam-70\%; bentonite-30\% & 1555 & 9.8 & 2.1 & The specimen has \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Compositions of the charge and properties of products with the addition of bentonite clay. The addition of 10, 15, and 20% bentonite slighty decreased the average density of the samples by 3.5%, 4.7%, and 3.2%, respectively. With the addition of 10 and 15% bentonite, the compressive strength increased by 22.7% and 22.9%, respectively.