OP asks "..how to determine the impact ...?"
My suggestions:
[a] Measure it by doing a MIL-STD-2105 Fragment Impact Test. (If you are government or a gov't contractor, DOD activities routinely do this. Cost is in 4 digits.)
Estimate it via empirical equations available in open source literature, e.g. google search the words "hertz concrete impact" to find journal papers.
[c] check out textbooks in explosive effects, rock blasting, terminal ballistics, etc.
The specifics will depend on the many variables mentioned in the previous posts.