Recently, in the framework of H2020, the European Commission has funded the project ReSHEALience (www.uhdc.eu), whose main goal is to develop an Ultra High Durability Concrete (UHDC) and a Durability Assessment-based Design (DAD) methodology for structures, to improve durability and predict their long-term performance under Extremely Aggressive Exposures. The project, coordinated by Politecnico di Milano, gathers 14 partners from 8 different countries (Italy, Spain, Estonia, Germany, Greece, Ireland, Israel, Malta), including 6 academic and research institutions together with 8 industrial partners, which cover the whole value chain, from producers of concrete constituents to construction companies to stake-holders and end-users. A key activity of the project will consist in the development of a theoretical model to evaluate ageing and degradation of UHDC structures, extending the modelling to predict the lifespan, and its incorporation in a Durability Assessment-based Design (DAD) methodology, which will be validated against experimental tests performed in the same project and the monitored performance of six full-scale pilots in real exposure conditions. The paper, starting from a review of the current state of art on the modelling of advanced cement based materials in extremely aggressive environments (EAE), will address the approach pursued in the project.