Questions related to Non-Destructive Testing
What is Non Destructive Testing?
Non Destructive Testing is defined as a method used to
investigate the integrity of an object, material or system,
without impairing its future usefulness.
Why is NDT used ?
It is used to determine the following : a) In place quality of
Concrete b) Health of Concrete] c) Influence of Time d) Non
availability of old drawings related to the structure.
How does Pulse Velocity Method work?
Usually if material differences in Pulse Velocity are found
within the structures for no apparent reasons, there is strong
reason to presume that some defective or deteriorated concrete
is present. High pulse velocity implies good quality of
concrete.
What is the co-relation between strength obtained through
concrete test hammer and CTM?
There is no standard co-relation . One has to generate a site
specific co-relation for each site/mix design.
NDT Survey are reconnaissance surveys. They are not exact. Under ideal conditions,. the accuracy of profometer using depth probe is: Upto 85 mm depth - + 1 mm Upto 85 - 100 mm - + 2 mm Upto 100 - 170 mm - + 5 mm Upto 170 - 200 mm - +10 mm Upto 200 - 240 mm - +20 mm Upto 240 - 300 mm - +30 mm
Can it detect mesh of rebars with diameter?
Yes, it depends on the experience of the user. One can detect the mesh with diameter and different levels of rebars.
What is the Accuracy?
The accuracy of the diameter measured increase with decrease in cover. It also depends upon the diameter of the bar. For example if the cover is 30 mm and bar diameter is 25 mm the accuracy is + 1 mm. This accuracy can improve if either of these parameters i.e. diameter or cover is reduced.
