Evaluation of the strength characteristics of concrete is an important criterion for the quality of building structures when examining the engineering and technical condition of buildings with a monolithic reinforced concrete frame. The main controlled indicator when assessing strength is the class of concrete by compressive strength, determined in accordance with GOST 18105-2018 by statistical processing of test results by destructive or non-destructive methods. The article assesses the methods used to control the strength of concrete in buildings under construction or in operation, provides the main requirements for the tests carried out, gives examples of the necessary equipment, and presents the most rational algorithm for assessing strength. The research materials will be useful for specialists in the field of construction and researchers dealing with issues of the quality of building materials.

Keywords: non-destructive testing, concrete compressive strength, concrete testing, concrete class, calibration dependence, monolithic structures