ABSTRACT
The work shows that the shape of a concrete specimen influences its strength indicators. When the shape is changed, the influence of individual defects and the quality of the structure on the size of the working section and, consequently, the final value of the strength indicators, changes. The heterogeneity of the structure of concrete leads to the fact that when it is loaded, no pure compression, tension or shear stresses are observed. Normal and tangential forces of adhesion are the weakest in concrete. Therefore, in any test, it is destroyed by stretching or shearing forces. It is shown that concrete must be tested directly in structures and buildings without their destruction, determining the unconditional characteristics of the strength of the tested concrete sample, and physical and mechanical properties of concrete should be tested in a certain place of a specific structural element.
