## 2 Materials and Methods
### Methods  
For the preparation of centrifuged samples, an experimental laboratory centrifuge was used, a schematic diagram of which is presented and described in detail in [34]. In addition, in [35; 36] the mode of forming samples of centrifuged concrete is described in detail. For the manufacture of vibro-centrifuged samples, an experimental laboratory vibro-centrifuge was used, a schematic diagram of this installation and a detailed description are presented in [37]. In addition, in [13; 32; 37] the mode of molding of prototypes of vibro-centrifuged concretes is described. This study applied:  
* Technological equipment--laboratory concrete mixer BL-10 (LLC \"ZZBO\", Zlatoust, Russia); laboratory vibrating platform SMZh-539-220A (LLC \"IMASH\", Armavir, Russia); planetary ball mill \"Activator--4M\" (LLC \"Chemical Engineering Plant\", Novosibirsk, Russia) (Figure 2). * Testing equipment--hydraulic press IP-1000 (OOO NPK TEKHMASH, Neftekamsk, Russia), tensile testing machine R-50 (OOO IMash, Armavir, Russia). * Measuring instruments--stationary pH meter Starter 2100 (OHAUS CIS, Moscow, Russia) measuring metal ruler 500 mm; laboratory scales; device for measuring deviations from the plane NPL-1; device for measuring deviations from perpendicularity NPR-1. In total, four basic samples of annular cross-section were manufactured and tested with the following dimensions:  
* Outer diameter D = 450 mm;
* Inner diameter of the hole d = 150 mm;
* Total height H = 1200 mm. Figure 2: General view of the planetary ball mill “Activator—4M”. The basic samples were concrete samples obtained using a specific technology, from which prototypes were subsequently made and tested. In the case of vibration technology, the samples were formed from a concrete mixture ready for testing immediately--cubes and prisms. In the case of centrifugation and vibro-centrifugation technologies, prototypes (cubes and prisms) were obtained from the base samples of the annular section by the sawing method. One series of samples of annular section corresponds to one type of activation and includes three basic samples of annular section for each manufacturing technology (centrifugation and vibro-centrifugation). That is, a total of 12 samples of concrete of annular section were made by centrifugation and 12 samples by vibro-centrifugation. The technique for manufacturing prototypes of vibrated, centrifuged and vibro-centrifuged concretes is presented in [37]. Freshly formed samples of the variatropic structure are shown in Figure 3.  
In total, 3 series of samples of each type of technology were manufactured and tested. Each series consisted of 6 samples for one type of test to obtain sufficient statistical reliability of experimental studies:  
* Type of concrete production technology--vibration: 24 cube specimens 15 cm \(\times\) 15 cm \(\times\) 15 cm in size for testing for cube strength (4 types of activation \(\times\) 6 cube specimens); and 72 prism specimens measuring 15 cm \(\times\) 15 cm \(\times\) 60 cm for testing prismatic strength, flexural tensile strength and axial tensile strength (4 types of activation \(\times\) 6 prism specimens \(\times\) 3 types of tests);
* Type of concrete production technology--centrifugation: from 12 basic samples, 24 cube samples 15 cm \(\times\) 15 cm \(\times\) 15 cm in size were cut out on a stone-cutting machine for testing for cube strength (4 types of activation \(\times\) 6 cube samples); and 72 prism specimens 15 cm \(\times\) 15 cm \(\times\) 60 cm for testing prismatic strength, flexural tensile strength and axial tensile strength (4 types of activation \(\times\) 6 prism specimens \(\times\) 3 types of tests);
* Type of concrete production technology--vibro-centrifugation: similar to centrifugation. Figure 3: General view of freshly formed samples of variatropic structure. In total, 288 prototypes were manufactured and tested--cubes and prisms. Samples before testing hardened for 28 days.