This article considers the problem of thickness measurements and flaw detection in concrete with one side access. It can be solved by ultrasonic echo methods based on the application of multiple-unit antenna arrays, with further data processing in accordance with tomographic algorithms. The data processing algorithm and criteria of the selection of antenna arrays parameters, based on experimental investigations, are described in the article. The results of concrete inner structure inspection obtained by the proposed method are presented. Practically, it is possible to receive an image of concrete cross section at depths of up to one meter and to detect hollow defects with diameters of more than 50 mm.