# Influence of Variotropy on the Change in Concrete Strength under the Impact of Wet-Dry Cycles
## 5 Conclusions  
Based on the results of assessing the effect of alternating wetting and drying on concretes made using various technologies--vibrating, centrifuging, and vibrocentrifuging, the following conclusions can be drawn.  
1. With an increase in the number of moistening and drying cycles, at first there is a slight increase in the strength characteristics of the samples, and then there is a decrease.
2. The loss of cubic compressive strength after 600 wet-dry cycles for vibrating concretes was 36% at pH 5, 20% at pH 7, and 23% at pH 10; for centrifuged concretes, the cubic compressive strength decreased by 28% at pH 5, by 14% at pH 7 and by 18% at pH 10. For vibrocentrifuged concretes, the reduction in cubic strength was 21%, 10%, and 15% for pH 5, pH 7, and pH 10, respectively.
3. The prismatic compressive strength decreased similarly to the cube strength: the losses at various levels of pH 5, pH 7 and pH 10 were 37%, 22%, and 22% for vibrated concrete, 26%, 15%, and 18% for centrifuged concrete, and for vibrocentrifuged concrete, 20%, 11%, and 14%, respectively.
4. An acidic medium has the most negative effect on the strength characteristics of concretes made using various technologies, compared with neutral and alkaline media. The loss of strength of concrete when moistened in an acidic media was greater than in an alkaline and especially neutral media.
5. Vibrocentrifuged concrete turned out to be more resistant to aggressive environments and moistening and drying cycles than centrifuged and vibrated concrete. The drop in strength was up to 7% less compared to centrifuged concrete and up to 17% less than vibrated concrete.
6. Prospects for the practical application of the results obtained lie in the manufacture of real factory centrifuged and vibrocentrifuged reinforced concrete structures with a study of the possibility of using smaller grades for water resistance and lower consumption of materials, taking into account the fact that an additional protective effect will be created in the protective layer of concrete by creating variotropically improved vibrocentrifuged and centrifuged concrete structures.
7. Prospects and directions for the development of research are seen in checking the water resistance and resistance to moisture and drying of concretes of higher classes and densities, as well as concretes with reduced density, lightened using porous aggregates, or combined aggregates.  
Conceptualization, S.A.S., E.M.S., D.E. and A.C.; methodology, S.A.S., E.M.S. and A.P.; software, S.A.S., E.M.S., A.N.B. and A.C.; validation, A.C., S.A.S., E.M.S. and D.E.; formal analysis, A.C., S.A.S. and E.M.S.; investigation, D.E., A.P., L.R.M., S.A.S., E.M.S., A.N.B. and B.M.; resources, B.M.; data curation, S.A.S., E.M.S. and A.C.; writing--original draft preparation, S.A.S., E.M.S. and A.N.B.; writing--review and editing, S.A.S., E.M.S. and A.N.B.; visualization, S.A.S., E.M.S. and A.N.B.; supervision, L.R.M. and B.M.; project administration, L.R.M. and B.M.; funding acquisition, A.N.B. and B.M. All authors have read and agreed to the published version of the manuscript. This research received no external funding.  
Not applicable.  
The study did not report any data.  
**Acknowledgments:** The authors would like to acknowledge the administration of Don State Technical University for their resources and financial support.  
**Conflicts of Interest:** The authors declare no conflict of interest.