## 2 Materials and Methods
### Main Research
#### 3.2.2 Compressive and Bending Strength Tests  
Unlike the preliminary study, which conducted strength tests on three specimens, the main study performed tests on eight specimens to achieve a statistical indicator. Figure 4a presents the results of the compressive strength tests, while Figure 4b displays the results of the bending strength tests. Figure 4c illustrates the percentage increase in strength of samples with polyfractional cements compared to the reference sample. Figure 4d presents the coefficients of variation in the data points, characterizing the reliability of the results obtained. According to the test results, an increase in compressive and bending strength is observed in all SCC compositions (Types 2-7) using a polydisperse binder. Depending on the composition, the compressive strength varies from 49.31 to 53.92 MPa, while the strength of the reference sample is 42.76 MPa. In percentage terms, the strength increases by 15.3 to 21.7%. The bending strength varies from 5.41 to 5.74 MPa, and the strength of the reference sample is 5.16 MPa. In percentage terms, the increase ranges from 4.8 to 11.2%. The increase in strength characteristics can be explained primarily by a rise in the packing density of binder particles from 0.564399 (type 1) to 0.593257 (Type 7) and a decrease in the content of ettrintite Ca\({}_{3}\)Al\({}_{2}\)O\({}_{6}\cdot\)3 CaSO\({}_{4}\cdot\)31H\({}_{2}\)O and portlandite Ca(OH)\({}_{2}\) in the composition of the polydisperse binder, which is consistent with the results of [27]. The use of a polydisperse binder promotes more intensive hydrolysis and hydration processes of cement particles in additionally formed crystallization zones. This fact is confirmed by data obtained during a study using the X-ray phase analysis method of cement stone [29]. When using three-component compositions (Types 5-7), a slight increase in compressive strength by 5-6% and in bending by 3-4% is observed in relation to two-component compositions (Types 2-4), which, apparently, is in direct dependence on the packing density of the polydisperse binder and, accordingly, a decrease in the micropores of the cement stone. The results obtained are also consistent with the results of [30]. If we consider the dynamics of the change in the strength of samples with three levels of dispersion (Types 5-7), we can observe a decrease in the intensity of the increase in strength from an increase in the content of particles of the smallest fraction F3. If the strength of Type 6 samples in relation to Type 5 samples increase by 3.48% (under compression) and by 2.35% (under bending), then the strength of Type 7 samples in relation to Type 6 samples increase by 0.26% (under compression) and by 1.41% (under bending). The coefficients of variation in the datapoints in compression tests vary from 3.03 to 5.45%, and in bending from 5.23 to 7.32%. In both cases, the maximum scatter of datapoints is observed in the reference sample tests. The latter is understandable, since samples of types 2-7 have a more ordered structure of fractions, in contrast to samples of type 1, in which sintering of particles or statistical error in the size of fractions in a batch may occur. In any case, the obtained variation coefficients are within the acceptable value sand do not exceed 13.5% [31], which indicates a high degree of reliability of the obtained strength