## 3 Results and Discussion
### Discussion
In addition, the high efficiency of vibrocentrifugation is confirmed in [35; 36; 37; 38; 39; 40]. In general, vibrocentrifugation, being a developed stage of the centrifugation process, and its high effect are in good agreement with [42; 43]. As for vibrated concrete, in this case, it is technologically difficult to achieve positive variotropy due to the peculiarities of compaction by vibration. Therefore, for vibrated structures, it is recommended to use the traditional method of increasing the resistance to sulfate attack through recipe methods. These can be specified dosages, compositions, or the use of special additives that will slightly increase the resistance to sulfate attack of vibrated concrete, if necessary. However, we repeat that, technologically, the greatest efficiency for operation in such conditions was shown by vibrocentrifuged concrete. Let us explain the physical essence of this process. As we have already proved earlier [34; 41], the structure of such concrete has a more perfect form, both at the level of microporosity and at the level of macroporosity. The porous structure of the outer layer, which is a protective shield for the entire structure, allows it to withstand corrosion phenomena and impacts and protects weaker inner layers, including those in which reinforcing elements are located. Thus, an additional emerging compacted layer, which is also present in centrifuged concrete, but is most pronounced in vibrocentrifuged concrete, creates structural and technological protection, and thus, the destructive mechanism of sulfate attack is slowed. Figure 13 shows a sample sawn from a concrete sample of an annular section, where one can visually observe the characteristic previously selected layers. Thus, we have technologically and experimentally proven the advantages of vibrocentrifuged concrete technology. This technology is proposed for implementation in structures operating in special conditions with an increased risk of sulfate attack in concrete and reinforced concrete. If we talk about variotropic concretes made using centrifugation and vibrocentrifugation technologies, then the main means of increasing their corrosion resistance is to increase the average density of concrete. This can be achieved through the following recipe and technological solutions (Figure 14). Structure modification with the introduction of additives is an effective and widely used method for increasing corrosion resistance. The undoubted advantage of this method is the manufacturability and low cost of most additives. However, it should be borne in mind that the effect of additives in vibrated and centrifuged concrete may not be the same. The use of surfactants, organosilion liquids, and water-soluble resins does not exclude the formation of directional porosity--migratory pores and channels--in the inner layers of centrifuged products, which will not provide them with the required increase in the resistance of concrete and the service life of products and structures made of it. This necessitates a special assessment of the effectiveness of traditional additives under  
Figure 14: Ways to improve the resistance of variotropic concrete to corrosion. Figure 13: Concrete sample of variotropic structure. conditions of aggressive action on variotropic concrete. The greatest technical effect can be obtained by impregnating the hardened inner layer of concrete with a monomer followed by its polymerization. In centrifuged and vibrocentrifuged concrete, directional porosity is eliminated, which is its main drawback [59]. The obtained results and the developed dependencies can be used as the foundation for new normative and technical documents and updated standards. In general, this approach is aimed at optimizing construction and technical processes, saving material, economic, and labor resources in terms of a more accurate assessment of the durability and life cycle of reinforced concrete structures that have hidden reserves due to the phenomenon of variotropy.