In the framework of the ODOBA project, representative structures in reinforced concrete are submitted to various types of durability distress, in order to have elements of knowledge on pathologies which could develop in the course of time. Among studied issues are the alkaliaggregate reaction (AAR) and the delayed ettringite formation (DEF), which appear after a large induction period, but develop then quickly, inducing irreversible structure damage. These issues are closely related to the water distribution and to the surrounding humidity. Controlling the processes of drying and wetting of concrete is of major importance in this regard. However, the mechanisms at their origin are currently not well established and modelled. This work is a preliminary study aiming at identifying the main mechanisms in play during drying-wetting cycles through a coupled experimental-numerical study of the humidity gradient inside concrete. In this paper, the drying of various concrete samples is cautiously studied through refined measurement of the mass loss and internal relative humidity distribution. Various sample sizes and shapes are tested. A simulation strategy is described, including the modelling of water vapour diffusion and liquid water permeation. The introduction of a boundary layer at the drying interface improves the mass variation prediction.