Study of the resistance of concrete of anisotropic and varitropic structures to alternating wetting and drying

Objective: study of the influence of a number of operational factors on the final resistance of varitropic concrete to alternating cycles of wetting and drying. This work identifies the problem of concrete resistance to cyclic wetting and drying, and also formulates a scientific deficiency consisting in the inadequacy of the existing knowledge base regarding the relationship between the type of concrete structure and its resistance to cyclic influences, including alternating wetting and drying. Methods: test samples were made using three different technologies: vibration, centrifugation, and vibration centrifugation. The following main characteristics were studied: compressive strength, tensile strength in bending, water resistance. Experimental studies have shown that concretes with a varitropic structure (centrifugation and vibration centrifugation) have higher resistance to alternating wetting and drying than concretes with an anisotropic structure (vibration). After 500 cycles of wetting-drying and a high degree of aggressiveness of the saturated aqueous environment in terms of the content of sulfate, chloride and nitrate salts, the loss of compressive and tensile strength in bending for vibrated concrete was 28.7 and 32.7 respectively, for centrifuged concrete — 26.2 and 27.8%, respectively, and for vibrocentrifuged ones — 19.6 and 21.4 %, respectively. Results: Vibrocentrifuged varitropic concretes showed the greatest resistance to the effects of alternating wetting in an aqueous environment with varying degrees of aggressiveness and drying compared to centrifuged varitropic and vibrated anisotropic concretes.