The analysis of the dependences of the "flexural strength – compressive strength" of ordinary concretes obtained as a result of processing numerous experimental data of the authors and borrowed from published works, as well as data presented in various regulatory documents is presented. Based on the obtained regression equations describing the dependence of the flexural strength of concrete on the compressive strength in the compressive strength range from 30 to 100 MPa, it is concluded that it is advisable to normalize the classes of flexural strength without taking into account the prescription features of concrete. Some inconsistency of the ratios of classes for flexural strength and compression in the analyzed regulatory documents has been revealed. The high reliability of the previously obtained dependence of the flexural strength of concrete on the compressive strength has been confirmed. A formula is proposed that takes into account the effect of the addition of silica fume in the composition of the concrete mixture on the ratio of flexural strength and compression. The role of the quality of aggregates in ensuring high flexural strength of concrete is noted.
Keywords: the flexural strength of concrete, the compressive strength of concrete, concrete strength classes, concrete for road and airfield coatings