This article is a focus on the anisotropic behavior of concrete under Alkali- Silica Reaction. In this article, we assume that the dense aggregates of a loaded concrete are attacked and progressively replaced by a swelling gel. Part of the gel escapes in the cement paste porosity but a pressure build-up still occurs. The pressure exerted first leads to decohesion between the aggregate and the cement paste, and second to a cracking of the cement paste. Microcracks are computed through an energy minimization algorithm, taking into account the effect of an external loading. The energy used is a modified poromechanics-type energy, taking the external loading and the reaction extent as state variables, which coefficients are determined through closed form solutions adapted from classical Eshelby solution-based micromechanics estimates.