This paper focuses on studying the consequences of expansion due to delayed ettringite formation (DEF) on transfer and mechanical properties of concrete in the case of nuclear structures. It concerns a concrete representative of a containment vessel of a nuclear power plant where temperature variations at early age are very large. An experimental heat treatment, representative of the temperature history in the raft foundation of the containment vessel was reproduced after a modeling of its temperature rise. After this treatment, concrete exhibits swelling due to the development of DEF. The gas permeability is increased significantly after swelling, and the safety requirements expected by these structures are thus affected.
