## 2 Materials and Methods
### Main Research  
#### 3.2.1 X-Ray Phase Analysis  
The X-ray phase analysis (XPA) method was used to study the phase composition of the polyfractional binder and to determine the degree of its hydration. Figure 3 presents the X-ray phase analysis of hydrated samples of cement stone and polydisperse binder after 28 days of normal hardening. Figure 3a-g display the results of the X-ray phase analysis of samples from types 1-7, while Figure 3h illustrates the diagram notation.  
Table 11 shows the phase composition of the investigated cement stone and polydisperse binder samples at the age of 28 days of normal curing, calculated based on the obtained data.  
The results of X-ray phase analysis showed that in the compositions of samples of type 5, 6, and 7 of polydisperse binder, the degree of hydration decreased from 71 to 61%, respectively. The decrease in the degree of hydration is explained by the presence of large binder grains that are not fully hydrated (fraction 1500 cm\({}^{2}\)/g), which form a reserve of clinker stock. The significant amount of unreacted alite and belite minerals (i.e., the clinker stock) is explained by the low reactivity of large (up to 100 \(\upmu\)m) cement particles, which are covered with a shell of new formations that slow down further hydration. The clinker stock in a polydisperse binder (the stock of coarsely dispersed particles is a fraction of 1500 cm\({}^{2}\)/g) should theoretically increase the durability of concrete made on its basis in the future [27].  
In the absence of a large fraction of 1500 cm\({}^{2}\)/g in the polydisperse binder (compositions of samples of types 2, 3 and 4), a decrease in the amount of clinker mineral C\({}_{2}\)S to 20% and an increase of up to 10% in the degree of hydration were observed in comparison with the reference sample. This effect is explained by the absence of a large fraction of 1500 cm\({}^{2}\)/g and the higher reactivity of the fine fraction of 4500 cm\({}^{2}\)/g, which accelerates the hydration of the binder; this leads to a higher degree of hydration in the early stages and, consequently, higher compressive strength [27]. The latter was confirmed by the results of the preliminary stage of the strength study (Table 9). This is due to the formation of a denser phase C-S-H, containing a smaller amount of water, and as a consequence, a decrease in the amount of portlandite Ca(OH)\({}_{2}\), as well as the formation of a smaller amount of ettrinigite. In the composition of the polydisperse binder, an increase in the content of the amorphous phase is recorded compared to the control sample of hydrated cement. This effect causes the presence in the composition of the polydisperse binder of an increased amount of non-crystallized new formations, represented by ortho- and diorthohydrodisilicates. These compounds, in turn, at later stages of hydration are transformed into crystalline hydrosilicates of the tobermorite series, such as (tobermite, xonotlite, foshagite, etc.). The data obtained are consistent with reference data and the results of previous scientific works [27; 28].  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Types**} & \multicolumn{3}{c}{**Composition (Component Content), \%**} \\ \cline{2-3}  & **F1** & **F2** & **F3** \\ \hline Type 1 & \multicolumn{3}{c}{Reference sample} \\ Type 2 & 80 & 20 & 0 \\ Type 3 & 75 & 25 & 0 \\ Type 4 & 70 & 30 & 0 \\ Type 5 & 15 & 80 & 5 \\ Type 6 & 15 & 75 & 10 \\ Type 7 & 15 & 70 & 15 \\ \hline \hline \end{tabular}
\end{table}
Table 10: Compositions for the main research.  
Figure 3: The results of the X-ray phase analysis: (**a**) Sample 1; (**b**) Sample 2; (**c**) Sample 3; (**d**) Sample 4; (**e**) Sample 5; (**f**) Sample 6; (**g**) Sample 7; (**h**) Notation.