Concrete field investigations are the gravity center of the senior author's activity since the 60s. Calibration curves in plants for precast elements using as well ultrasonic pulse velocity and attenuation respectively, as the Schmidt rebound hammer, field investigations on different building sites (road and railway bridges, different constructions etc. ) in order to assess the quality of the concrete are some examples. A very important author's contribution is to have quantified the influence of the hardening conditions (especially of different hydrothermal treatments) on the relation between the concrete compressive strength and the values measured nondestructively. Related to the hydrothermal treatments must be mentioned the use of ultrasonic pulse vibrations for the optimization of treatments cycle. A further development also successfully used are the so- called "combined NDT-methods".

Among the -ray-examinations, there are presented the particular cases of examination of welding in a depth of about 100 meters below sea level and of welding joints at a large heat exchanger. It is to be mentioned that, in order to be able to make statements on the quality of the gamma radiography, it was necessary to develop special penetrometers. Special problems resulted for the investigation on welded ovoid pipes.

A supplementary technique used, which allows viewing into structures (containing cavities) by means of small drilled access holes, is the endoscopy with fiberscopes and boroscopes respectively.