Introduction
Non-Destructive Testing (NDT) plays very important role in assessing structural properties of various materials used in the bridges and also integrity of various structural members of the bridge and the capability of these structural members to cater to the load which are expected to. Load rating of existing bridges, structural stability for increased load, and effectiveness of repairs are some of the areas where NDT plays a major role.
Non Destructive Testing (NDT) is being practised in India for around three decades or more by now. Most of the NDT techniques available across the world in developed countries are available in India. The fact remains though, that there are very few Laboratories which have a complete range of NDT equipments required for testing of the structures, particularly Bridges.
The non-destructive evaluation techniques are being increasingly adopted in concrete structures for the following purposes:
- Estimating the in-situ compressive strength.
- Estimating the uniformity and homogeneity.
- Estimating the quality in relation to standard requirement.
- Identifying areas of lower integrity in comparison to other parts.
- Detection of presence of cracks, voids and other imperfections.
- Monitoring changes in the structure of the concrete which may occur with time.
- Identification of reinforcement profile and measurement of cover, bar diameter, etc.
- Condition of prestressing/reinforcement steel with respect to corrosion.
- Chloride, sulphate, alkali contents or degree of carbonation.
- Measurement of Elastic Modulus.
- Condition of grouting in prestressing cable ducts.