Actually, there exists no well-defined and sufficiently precise investigation method to determine the quantity of cement in a hardened concrete.
In absence of an European norm, the Belgian labs refer today to the NBN B 15-250 proposing a method to calculate the amount of cement, based on the chemical analysis of the concrete.
However, the actual version of this norm has numerous limits and is only representative if the cement and the other constituents of the concrete are available or known.
Indeed, if the cement is not known, which is the most usual case, it is supposed to belong to one of the three reference cement categories proposed in the Belgian standard.
But, at the moment, there exist 27 cement categories (according to the European standard EN 197-1) of which 13 are frequently used in Belgium.
For economic and environmental reasons, the most used cements today have a certain part of the clinker substituted by other constituents such as fly ashes, blast-furnace slag or limestone fillers whose presence makes the analyses very complex.