The decision on this depends on the question to which the engineer wishes to have an answer. Several questions are possible. The two most common are: does the con- crete comply with the specifica- tion? and, what is the compressive strength of concrete in the struc ture in general? To answer this, cores should be taken at a number of locations spread over the whole Structure. But there is a caveat: concrete in the uppermost part of any member or concrete lift is nearly always weakest and, there- fore, nonrepresentative. There may also be this question: is the strength of the particularly highly-stressed parts of the struc ture adequate? In such a case, the locations for core-taking should be carefully chosen so that the load- carrying capacity of the structure 15 not impaired by removing some Concrete from the place where it is most needed. It follows that only an engineer familiar with structural