French term (edited): mat�riau pleine masse

So "coring of mass concrete" and "density of mass concrete". As opposed to coring and density of concrete in other locations where it is not so thick.

Basically mass concrete is that which is so thick and highly dosed in cement that it requires special treatment to deal with the heat of hydration and risk of cracking. Nuclear power plants tend to have plenty of such concrete!

Without changing the translation, it might also imply that this "mass concrete" or first-phase concrete is that subsequently covered in detail concrete or second-phase concrete, generally a finer-grained concrete that is easier to cast into complicated shapes as may be required on the finished walls and floors.