The present work focuses on the impact of the chemical degradations of cementitious materials such as Delayed Ettringite Formation (DEF) on the overall material properties. DEF is an endogenous pathology due to the crystallization of ettringite within voids and cracks. The crystallization pressure in the porous cement paste induces swelling and cracking by differential expansion. The study aims to characterize the evolution of effective material properties (diffusion coefficient, apparent tenacity) with respect to DEF. A non-linear chemo-mechanical modeling is proposed where the entire diffusion-precipitation-pressurization-crack process is solved in a staggered approach. The diffusion-precipitation mechanism is translated by a rough chemical model. The resulting local volume fraction of ettringite is estimated by a finer micro-mechanical-based model using the effective elastic properties of the cement paste. The crack initiation and propagation is estimated with a dedicated cohesive zone model including pressure effect. Some applications of the model are presented.