[jaden]

the usage of destructive testing methods on pre-cast concrete products depends
1. on the standards applicable to the product in the respective country and
2. on the techniques the manufacturer has found useful for quality control. There is a wide range of possibilies.

Concerning non-destructive methods, I am not aware of any standards. Ultrasonic through transmission has been used for quality control for a long time. Changes of the pulse velocity indicate variations in the manufacturing process, cracks, or other problems.

During the last few years non-destructive testing methods have been developed further. As an example, our institute conducts R&D on ultrasonic methods. It is now possible to measure pulse velocity without surface contact employing air-coupled transducers, or to image concrete elements from one side using electronic and mechanical scanning and 2D or 3D SAFT reconstruction.