Engineering clay barriers are one of the main solutions considered for the containment of waste, both within the context of landfills and, in perspective of longer operational times, of nuclear waste disposal. Modeling the performance of these barriers in the long term can be difficult, since the behavior of active clays highly depends on variables such as temperature, degree of saturation and suction, and chemistry of the wetting fluid.This paper deals with the effects of chemical changes. Based on microstructural evidence, a double structure model for coupled chemo-hydro mechanical processes is formulated. The model is then used to reproduce a salt transport test run in oedometer conditions. Some implications of the proposed double porosity approach are highlighted and discussed. The frame has the advantage of being based on direct microstructural evidence and of allowing for joint interpretation of hydro and mechanical changes. The frame also shares characteristics with models used to reproduce the behavior of clays in unsaturated conditions, so making it appealing for its implementation within a wider context.