## 2 Materials and Methods
### Methods
* A total of 12 series of tests were carried out; for each series of tests, 3 cube samples 50 \(\times\) 50 \(\times\) 50 (mm) in size and 3 prism samples 50 \(\times\) 50 \(\times\) 200 (mm) in size were made. Thus, the total number of samples for cubes was 117, 9 controls (3 vibrated, 3 centrifuged, 3 vibrocentrifuged) and 108 for cyclic tests (36 vibrated, 36 centrifuged, 36 vibrocentrifuged). The total number of prism samples, similar to the number of cube samples, was 117. * For the manufacture of vibrated concrete, a concrete mixture with a mass ratio of SRPC:sand:crushed stone:water = 1:1.3:2.6:0.52 was used [46], and for the manufacture of centrifuged and vibrocentrifuged concrete [47], a concrete mixture was used with a mass ratio of SRPC:sand:crushed stone:water = 1:1.44:2.48:0.41 (concrete mixing proportions in 1 m\({}^{3}\) are given in Table 6);  
Figure 2: The process of moisturizing concrete samples in 5% Na\({}_{2}\)SO\({}_{4}\) solution. At the same time, the properties of the fresh state of vibrated, centrifuged, and vibrocentrifuged concrete almost did not differ from each other. The fresh state properties of vibrated, centrifuged, and vibrocentrifuged concretes are presented in Table 7.  
Samples for determining the fresh state properties of concretes are shown in Figure 3.  
* Production of vibrated, centrifuged, and vibrocentrifuged concretes, as well as sawing of variotropic concretes, was carried out according to the method presented in [34]. Photos of specimens for compression tests before failure and after are shown in Figure 4.  
Compressive testing of specimens was carried out according to GOST 10180-2012 [50] and GOST 28570-2019 [51] for cube strength and according to GOST 24452-80 [52] for prismatic strength. The assessment of the concrete corrosion resistance in an acid solution (continuous sulfate attack), for samples made using the technologies of vibrating, centrifuging, and vibrocentrifuging, is based on the rate of change in the chemical composition of the H\({}_{2}\)SO\({}_{4}\) acid solution and hardened cement paste in concrete immersed in a 5% concentration (pH equal to 4 \(\pm\) 0.1) acid solution during diffusion transfer of an aggressive substance in concrete. The test was carried out at a temperature of 20 \(\pm\) 3 \({}^{\circ}\)C as follows [53; 54]:  
* The samples were prepared in advance; namely, their side surfaces were covered with a protective coating. Then the prepared samples were placed in desiccators and filled with an acid solution. The distance between the working surfaces of the samples and neighboring samples, as well as to the surface of the mortar, was at least 2 cm. In total, 12 samples 50 \(\times\) 50 \(\times\) 50 mm in size were made for each type of concrete. The process of curing concrete samples in a sulfuric acid solution is shown in Figure 5.
* Before testing and periodically during testing, the acid concentration was determined by acid-base titration. Immediately before sampling, the acid solution was stirred; when the acid concentration decreased by 5 \(\pm\) 0.1% compared to the initial acid solution, it was replaced with a new one. * The total duration of testing samples was 180 days. In the first three weeks of testing, samples of the acid solution were taken and titrated daily; then, three times a week; and after 3 months of testing, twice a week. When processing the test results, the amount of acid that entered into a chemical reaction with concrete was determined, and the amount of Ca\({}^{2+}\) ions that entered into a chemical reaction with acid was calculated.