Internal swelling reactions are concrete pathologies that cause expansions in the structure and may lead to degradations. The origin of this swelling is attributed to the Delayed Ettringite Formation (DEF) in case of the Internal Sulfatic Reaction (ISR), if the temperature of the concrete at early age has exceeded 65°C, or to a gel, in case of the Alkali Silica Reaction (ASR) or Alkali-Aggregate Reaction (AAR) if the aggregate is reactive. They can appear in the civil engineering structures several decades after their construction under certain thermodynamic conditions. In the nuclear field, this risk is not excluded, especially in case of massive structures, such as containment building, which are considered as non-replaceable elements of a Nuclear Power Plant (NPP). Therefore, assessment of their behavior is of primary importance, as they represent the third and last containment barrier against the possible release of radioactive products into the environment.