The small specimens have been in general used in non-destructive testing of concrete. However, there may be significant differences in the quality of concrete between the specimens and in situ concrete because of the difference in the methods of compacting, curing of concrete and moulds, etc. In this paper, non-destructive test techniques, such as measurements of ultrasonic pulse velocity through the concrete, the thermography and the radiography were used to detect regions of defects of in situ concrete up to the age of 2 months from immediately after compacting of the concrete. The specimens used in this investigation were four reinforced concrete beams with a nominal height of 1 200 mm, a web width of 500 mm and a length of 1 200 mm. The effects of defects were simulated by casting with three conditions : well compacted concrete with man-made defects ; no compaction ; and not well compacted concrete. Plywood panels and permeable panels for the concrete form were used.
