Deterioration of cementitious materials by sulfate ions is a concern for concrete in contact with ground water (and in a lesser extent sea water) in many parts of Europe, and is an important issue for underground construction identified as a major area for progress in the construction industry. Sulfate resistance relates closely to testing and standardization and therefore to prescriptive approaches. The lack of feed back oil the durability of structures made of blended cements makes it difficult to fit these new concretes with existing test methods and performance criteria. This paper concerns the microstructural Study of field samples and structures made of blended concretes available across Europe. This concerns several materials exposed to various climate regimes, ranging from Southern to Northern Europe (Spain, Germany, United Kingdom, Denmark and Norway). Complementary techniques Such as SEM, micro-XR-F, XR-D and PIXE are used to evaluate the microstructural performance and stability of the phase assemblage of those blended concretes in the case of sulflate (and chloride in some instances) ingress, compare to pure Portland concrete.