  A state coupling between the hydrostatic (volumetric) and deviatoric parts of
the free energy is introduced in a damage mechanics model relevant for the
quasi-brittle materials. It is shown that it describes the large dilatancy of
concrete under compression and the different localization angles and damage
levels in tension and compression. A simple isotropic description is used,
although similar ideas can be extended to anisotropic damage. The model is
identified with respect to tensile and compression tests and validated on
bi-compression and bi-tension. Fully written in three dimensions under the
framework of thermodynamics of irreversible processes, it allows further
developments within a finite element code.
