Evaluation of Long-term Performance of a Structure Using Non-Destructive Testing Techniques

Abstract

Non-Destructive Testing is the technique which permit testing of materials and structures without impairing the usefulness and performance of the structures. Non-Destructive Testing (NDT) Techniques have been used since last 20 to 25 years. These techniques have been adopted for various applications and for variety of structures. The various applications of NDT Techniques include assessment of overall quality/strength of concrete, diagnosis and categorization of distressed structures and ascertaining existing condition of concrete. NDT techniques are also widely used to check performance of repairs. IS 456-2000 has also stipulated the use of some of NDT techniques under clause of inspection and testing of structures. Preliminary investigation of a distressed structure has to be carried out before application of NDT. The preliminary investigation consist a detailed visual inspection. Considering the findings of the preliminary investigations, it is to be decided to carry out appropriate NDT techniques at selected locations so that more representative idea about the present state of the structure as well as the extent of the damage could be obtained. Non-Destructive testing results can give better idea about quality of concrete. To correlate NDT results with in-situ concrete strength, one need to establish correlation between NDT results and in-situ concrete strength. Many of the NDT equipment manufacturers provide charts or tables to correlate results and concrete strength, but as many factors affect NDT results, the given correlation can not be applied in any condition. Ultrasonic Pulse Velocity test and Pull out test have been proved very effective Non-Destructive testing techniques to assess quality and in-situ strength of concrete. Though Pull-out test is semi destructive test, it can be considered as NDT technique because it does not impair strength and stability of structure.