Radiographic testing of prestressed concrete structures

The roof structure was tested of a textile manufacturing hall consisting of 11 trusses of prestressed concrete of the SPPG-18 type with a span of 18 m. The axial distance of the girders was three metres. The distribution was studied of the prestressed reinforcement of the trusses and the level of the filling of ducts with injected mortar. A 60Co source with an activity of 1.1322 TBq (29.1 Ci) was used for radiographic inspection. The radiograms were made on Agfa-Gevaert D 7+Pb films and an MD-100 microdensitometer was used for evaluation. The testing showed that of the total number of 24 checked ducts only seven had been properly injected, 14 had been incompletely injected and in three cases the quality of injecting could not be assessed. A highly irregular distribution of cables was found. Next to the radiographic check a phenolphthalein test was made to detect the level of carbonized concrete. Also checked was the strength of the concrete. (E.S.)