Need of Non-Destructive Testing
Information about the in-situ strength of concrete may be required for both under construction as well as existing concrete structures. For new concrete structures under construction, N.D.T.may be required under following circumstances:
- Non-compliance of the material supplied in terms of works specimen test results or other specified requirements.
- Uncertainties concerning the level of workmanship involved in construction operations affecting the hardened properties of the in-situ concrete.
- Quality control of construction.
- Monitoring of strength development in relation to formwork removal, curing, prestressing,load application or similar purposes.
Existing concrete structure require an examination under the following circumstances:
- Deterioration of the concrete due to factors such a external or internal chemical attack,fire explosion and other environmental effects.
- To make assessment of the load carrying capacity of an existing structure for change of ownership or insurance purpose or in relation to a proposed change of use or alteration.
Advantages of Non-Destructive Testing
Non-destructive methods have following distinct advantages over the prevalent destructive methods of testing.
- The measurement can be done on concrete in-situ and thus representative samples are not required. In destructive method of testing the change in quality of concrete has to be studied on a long-term basis with respect to curing or deterioration due to certain causes.
A large number of specimens are required which could be tested to destruction, at various ages. Since it cannot be guaranteed that all specimens are of the same quality, the results obtained may not be very reliable.
- Non-destructive testing makes its possible to study the variation in quality of concrete with time and external influences.
- In N.D.T. method the concrete is not loaded to destruction. Its quality is judged by measuring certain of its physical properties, which are related to its quality.
- In N.D.T. there is no wastage of material as in destructive methods of testing.