Use of NDT in condition assessment of RC buildings

Condition assessment and serviceability of existing reinforced concrete (RC) buildings becomes a major issue especially when substandard material and workmanship quality are used. Low quality construction materials and methods accelerate especially the corrosion of the steel reinforcement and decrease the service life of RC structures, which should maintain a service life of at least 50 years according to the EN standards. Several 40-year-old RC buildings were investigated and their serviceability condition was determined based on non-destructive testing in conjunction with semi-destructive in-situ tests. Cores were taken from the structures to determine the mechanical strength and unit weight of in-situ concrete. Microstructural studies were performed on the thin sections and plane sections to evaluate the quality of materials and methods used in the construction. Non-destructive tests such as; Schmidt hammer, impact-echo and magnetic signals were used to determine the surface hardness of concrete members, cracks and voids within the concrete, location and size of steel reinforcement throughout the structure. Extensive carbonation and high level of chlorides were measured from the cores taken. Impact-echo measurements indicated high level of deterioration of concrete and damage. It has been shown that impactecho method could provide valuable information for the in-situ condition assessment of structures coupled with other experimental laboratory techniques.