## 5 Results and Discussion
#### 5.1.1 Research Results of the Integral Characteristics of Concrete
The modulus of elasticity in compression \(E_{b}\) and tension \(E_{bt}\) in the vibro-centrifuged concretes in comparison with the centrifuged and vibrated concretes at all times of hardening were up to 7.4% higher (see Table 2, Figure 17). An increase in the initial modulus of elasticity in compression and tension was explained by an increase in strength with a simultaneous decrease in the limiting strains of the vibro-centrifuged concretes in comparison with the centrifuged and vibrated concretes (Figure 18). Diagrams \"stress-strain\" under compression and tension in the vibro-centrifuged concretes in comparison with the centrifuged and vibrated concretes at all ages were characterized by the following features:  
1. The maximum shifts were up and to the left (strength increases, and limiting strain decrease);
2. The angle of rise at the origin of coordinates increases (initial modulus of elasticity increases). Thus, the tilt angle of the ascending branch increases in the diagrams, the descending branch is longer evident for the vibrated concretes, but for the centrifuged concretes and especially for the vibro-centrifuged concretes, it decreases (Figure 18). This picture was observed at all values of age of concretes. In Table 2, the corresponding deviations were calculated as follows:  
\[ \begin{split}\Delta_{1}&=\frac{\text{C}-\text{V}}{ \text{V}}\times 100\%,\\ \Delta_{2}&=\frac{\text{V}\text{C}-\text{V}}{\text{V }}\times 100\%,\\ \Delta_{3}&=\frac{\text{V}\text{C}-\text{C}}{\text{C }}\times 100\%.\end{split}  \tag{2}\]  
Corresponding parameters in (10) are related to vibrated (V), centrifuged (C) and vibro-centrifuged (VC) concrete samples. Study of Differential Design Characteristics of Centrifuged and Vibro-Centrifuged Concretes of Variatropic Sections  
As shown above, during centrifugation and vibro-centrifugation of samples with sufficiently thick walls, the centrifugal and centripetal forces acting on the outer, middle and inner layers of the cross-section are very different, which leads to a significant difference in the structure and characteristics of these layers of the sample, which in some cases must be taken into account in the calculations [42; 43; 44; 46; 47; 48; 49]. Therefore, after study of the influence of manufacturing technology (vibration, centrifugation, vibro-centrifugation) on integral (common) characteristics of concrete, we investigated the variatropy of the structure of experimental concrete samples of annular cross-section and the associated differential design characteristics of concrete layers. Since the previously obtained integral (common) results for all three technologies gave the characteristics averaged on cross-section of the concrete of the test samples as a whole, we also studied the characteristics of each of the three conditional separate layers (outer, middle and inner) of the test samples with the annular cross-section, the characteristics of which differed from each other due to centrifugation and vibro-centrifugation. Note that vibrated test samples for differential design characteristics were not investigated due to the absence of cross-section variatropy in them. Features of Experimental Research Methods for Differential Characteristics of Concrete by Ultrasonic Method  
Thus, with the exception of the vibrated test samples, the centrifuged and vibro-centrifuged samples in their cross-sections were variatropic, that is, they were a combination of conditional layers of one sample, the properties and characteristics of which differed from each other due to the manufacturing technology. The schedule and methodology for experimental studies of the differential structural characteristics of concrete have been detailed above. However, in order to obtain more detailed data, the following instrumental approach was additionally applied. To reveal the change in the properties of the samples in contact layers, we additionally applied ultrasonic sounding using the device Pulsar 2.2.