do u have Rebound no or Compressive strength?? because both are different thing, rebound no should be plotted in the graph to find the compressive strength. if u the calibrated value of rebound compressive strength u can go for the model.

I would tread carefully on this one.  Masonry behaves differently to concrete so you could be extrapolating beyond validity.  Ideally you should check the calibration against compressive strength tests on similar masonry.

Hello Kumar Pallav. Rebound hammer or combined methods with UPV is used for assessment and comparison of concrete's quality not for determination of its compressive strength. The results need to real compressive strength results measured from cores for satisfactory assessment or comparison. On the other hand, calibration of hammer should be done on their standard metalic plate not on concrete specimen. Moreover, carbonation reaction is making more brittle too old concrete surface, so the rebound number cannot be reliable on such surfaces. Another thing may be homogenity problem of old wall exposing varied external conditions in long term especially focused on its edges rather than other part of the wall.

Thanks Rahul

I have compressive strength and test are still in progress. Thank you for your suggestion.

 Thank you H. Süleyman and Baxter,

I will consider the same, as test are still in progress. I set the Hammer as suggested calibration curve given by the supplier.  It is having 3 curves viz., A, B, C. for which the range of compressive strength you expect. So we have set the range in lower range as the masonry is 102 year old. The problem is we cannot take a core from the building. We are also trying to findout dynamic modulus through UPV test at different location.

I understand that masonry behave very different. So I am trying to do some approximation in the model made in Ansys based on the test results.

Thank you for your suggestion 

i agree with Rahul Biswas .

 Absolutely not. The rebound curve must be calibrated by means of destructive tests on the tested masonry.

In our experience, the rebound hammer is not a reliable tool for determanation of mechanical properties, not even in concrete elements. We have mainly used it to assess homogeneity of the concrete in a same structure, using the corrected sclerometric values in a more qualitative than quantitave way.

I prefer to have calibration curves for the same material

Dear, the rebound hammer is suitable for checking the homogenity of concrete along the casted item, if the readings are not similar, then this indicates segration or non homogeneous concrete. It can be related to compressive strength by a number of laboratory test as supplied by the manfacturing company in terms of a curve or mathematical model.

If you like to consider it for masonary, then you need to have test on real masonary in the laboratory by traditional method and by thevrebound apparatus, then you can have the corelation.

Thanks Iqbal and Saad. 

rebound hammer number is a primary indication of concrete strength .This test depending on the many variables and not to be accurate to used in a numerical models alone .I recommend to use a pair of tests containing rebound with Ultrasonic Pulse Velocity.These two tests may be fabricated both in a numerical models to be more response and accurate.  

Ultrasonic test give more rational res;ts rather than hammer test.

Thanks Abbas, we are doing the test with ULTRASONIC.

Dear Kumar Pallav:

No, you can not relate old masonry (i.e. stone masonry) to concrete, May be you can do that for masonry from concrete units.

Did you made a comparison between hammer and ultrasonic test??

Given the stark difference between the two materials, particularly in porosity and homogenity, the results may not be reliable and hence a separate a calibration may be needed for numerical model. Furthermore, both UPV and Rebound Hammer methods need to be used carefully, as they may not yield reliable results in some cases. For a more candid discussion on the choice of these NDE techniques and their effect on reliability of results, you may refer to our article:

Article Non-destructive testing for in-place strength estimation of ...

Thanks.

It may be advisable to use combination of NDT techniques for masonry structures.

Calibration curves should be obtained for the same material

you should make calibration between R number and unaxial compression strength on core sample from the old rock

Thank you Hussien.