## 2 Materials and Methods  
### Materials  
The tuff used in the investigation came in the form of rock extracted from the deposits near Filipowice (region: Krzeszowice, Lesser Poland, Poland). It was crushed and then ground in an ultra-centrifugal laboratory mill RETSCH ZM1 (Retsch GmbH, Haan, Germany) to create grain sizes of less than 40 \(\upmu\)m. It was then roasted at 850 \({}^{\circ}\)C for 4 h to remove moisture and organic substances that could be emitted during sintering at 900 \({}^{\circ}\)C and thus contaminate the process. The experimental tuff contains sanidine as the main ingredient and small amounts of minerals such as kaolinite, biotite, illite, and quartz. The existing biotite grains are up to 8 mm in size while the other components have very different sizes from a few mm to 5 cm [23; 24; 25]. The tuff is a material with high porosity of about 23% and a density of 2.63 g/cm\({}^{3}\)[32]. The oxide composition of the tuff used is presented in Table 1.  
Porosymmetric analyses with the BET method showed that the value of the specific surface area of the tuff in its natural form is approximately 9708 m\({}^{2}\)/g [32]. These studies have shown that thermal processing of the tuff at 850 \({}^{\circ}\)C reduces the specific surface area of the tuff particles, reduces the volume of pores, and increases the average diameter of the pores, indicating the start of the sintering process [32]. To identify the components present in the tuff, and in particular, the type of carbonate binder that decays at temperatures close to 800 \({}^{\circ}\)C, XRD tests were carried out on a representative sample of the tuff in its natural state. The image of the registered diffractogram and the type of identified phases are presented in Figure 1[33]. \begin{table}
\begin{tabular}{c c c c c c c} \hline SiO\({}_{2}\) & Fe\({}_{2}\)O\({}_{3}\) & Al\({}_{2}\)O\({}_{3}\) & CaO & MgO & TiO\({}_{2}\) & K\({}_{2}\)O & Na\({}_{2}\)O \\ \hline
56.04\% & 5.38\% & 16.73\% & 5.39\% & 0.60\% & 0.85\% & 9.16\% & 0.39\% \\ \hline \end{tabular}
\end{table} 
Table 1: Oxide composition of the used tuff [32]. Figure 1: Results of the XRD analysis of the tuff under delivery condition: identified phases [33]. XRD research confirms that the SiO\({}_{2}\) and KAlSi\({}_{3}\)O\({}_{8}\) phases previously defined in the literature, the appearance of calcium carbonate CaCO\({}_{3}\) which is a carbonate binder, was identified in the tuff. The morphology of the tuff was analyzed on a JEOL JSM-820 (Tokio, Japan) scanning electron microscope with IXRF (IXR Inc., Austin, TX, USA). Before the test, small amounts of the materials were dried to constant weight and placed on a carbon bed. Next, the materials were sprayed with a thin layer of gold using a JEOL JEE-4X sputtering machine. The tuff was observed at high magnification--Figures 2-4. The morphology shows a tendency of the tuff particles to create agglomerations. This was taken into consideration during the mixing process; the planned mixing time was relatively long (12 h). Additionally, thermogravimetric analyzes were made for the tuff to check its applicability for planned solutions and proper parameterization of the sample preparation. Figure 5 shows the changes in the tuff weight as a function of temperature. It was observed that the tuff mass decreases with the temperature increases. At first, this effect is mainly related to the evaporation of moisture. Furthermore, water (\(m/z\) 17 and 18) is excreted from the sample in the temperature range from 30 \({}^{\circ}\)C to approximately 600 \({}^{\circ}\)C. Two maxima of water excretion are observed at the temperature of about 180 \({}^{\circ}\)C and the temperature of about 460 \({}^{\circ}\)C. In the first stage, the tuff is dehydrated, i.e., the absorbed water is removed, or possibly the inter-batch water is removed, while dehydroxylation is observed in the later stage.