In the framework of the H2020 project Reshealience, the modelling activity has dealt with the development of a model for Ultra High Durability Concretes at the mesoscale, accounting for both mechanical and hygro-thermo-chemical aspects. The model is being exploited in simulating the long-term performances in environments rich in chloride and sulphate in order to assess the ability of the numerical tool of catching the main degradation trends experienced by the material. In addition, an upscaling strategy has been set to make the mesoscale model the sound basis for engineering durability model at the structural level.