In situ non-destructive testing: the steel and concrete resistance assessment of 'ancient' r/c structures

摘要

The assessment of the mechanical properties of the materials of reinforced concrete structures by in situ non-destructive investigations are presented here. A series of in situ non-destructive tests has been performed with the purpose of investigating the mechanical properties of the basic materials (steel and concrete) employed in the civil buildings. The penetration resistance methods (Windsor probe system), the surface hardness methods, the ultrasonic method and combined methods were used to control the quality and estimate the strength of concrete in situ. The resistance obtained by the previous non-destructive methods is calibrated with the strength of cylindrical specimens (cores) extracted from some structural elements in the proximities of those considered to perform the non-destructive tests, by the least squares-method. The study gave prominence to: (ⅰ) large variations of the mechanics properties of the materials; (ⅱ) the better reliability of the combined methods; (ⅲ) the necessity to calibrate the resistance obtained by the non-destructive methods with the strength of the cylindrical specimens (cores) extracted from some structural elements in the proximities of the non-destructive tests; (ⅳ) for all the methods employed, the sensitivity decreases along with the actual strength.