NON-DESTRUCTIVE TESTING OF CONCRETE

This testing is conducted on the concrete as per IS 13311 – part 1 and 2 and is used to know:

1. The homogeneity of the concrete

2. The presence of cracks, voids and other imperfections,

3. Changes in the structure of the concrete which may occur with time,

4. The quality of the concrete in relation to standard requirements,

5. The quality of one element of concrete in relation to another

6. The values of dynamic elastic modulus of the concrete.

In this test method, if the concrete is not compacted as thoroughly as possible, or if there is segregation of concrete during placing or there are internal cracks or flaws, the pulse velocity will be lower, although the same materials and mix proportions are used.

The quality of concrete in terms of uniformity, incidence or absence of internal flaws, cracks and segregation, etc, indicative of the level of workmanship employed; can thus be declared by the below table, which have been evolved for characterising the quality of concrete in structures in terms of the ultrasonic pulse velocity.

The assessment of compressive strength of concrete from ultrasonic pulse velocity values is not adequate because the statistical confidence of the correlation between ultrasonic pulse velocity and the compressive strength of concrete is not very high. The estimated strength may vary from the actual strength by f 20 percent.  

The dynamic Young’s modulus of elasticity (E) of the concrete may be determined from the pulse velocity and the dynamic Poisson’s ratio as follows:

E ={ [Density of mix (1+ Poisson’s ratio) (1-2 X Poisson’s ratio) ] / (1- Poisson’s ratio) } X Square of pulse velocity.

Let see the testing method using REBOUND HAMMER TEST:

Conversion of rebound hammer no to compression test: Locate the reading as per the direction of test and read the Cop strength using this chart:

For more details about the Poisson's Ratio, watch this:

Let see the testing method using ULTRASONIC PULSE VELOCITY:

Let us understand the technique of ultrasonic pulse testing:

Let see the compression of results of ultrasonic, rebound and compression strength:

By the test result, may it be compressive strength, young’s modulus it shall match with the designed parameters tested in the lab by other direct methods.

Many thanks for google.com and www.masterbuilder.co.in from where the details are collected.