Will you make a study of the correlation of these two variables?. I mean if you will analyse the effect of heating the sample in the strength its fine that you can use the same sample. Otherwise, it will be better to have different samples of the same batch. Because the compression strength of concrete decreases as the heating duration increases so in this case as the sample will be heated the strength can be different of the sample without heating.

Dear Hammad,

This will affect your results in, unfortunately, unpredictable way. You might want to take a look at papers regarding compressive strength of concrete after exposure to elevated temperatures.

You can find a review here:

http://dx.doi.org/10.1016/j.conbuildmat.2015.05.131 (Fig. 1)

And some additional information in Neville's Properties of Concrete.

In my research, we noticed 11% rise of compressive strength when reference and oven-dried (105°C) samples were compared. You can find it here: https://www.researchgate.net/publication/325416491_Study_on_the_use_of_ultra-lightweight_cement_composite_for_enhancing_fire_performance_of_concrete_filled_tubular_columns (Fig. 1).

Best regards, Wojciech

You can, but your results will be affected. Therefore, not recommended.

The compressive strength of concrete will reduced when exposed to elevated temperature. The amount of strength reduction depends on many factors including type of concrete, compressive strength of concrete, heating rate, cooling rate etc. Hence, your cannot use the same samples.

Thanks to all for your reply.

Try both version. Test different samples for each property first and theb common samples for both properties to check the differences.