Safety of Nuclear Power Plants (NPP) is EDF main priority. Lifetime Extension Management, which is an industrial and economical objective thus requires solid demonstrations of NPP ability to sustain long term operation. Concerning the reactor containment building, an extensive research program is currently done, centered on a mock-up of a reactor containment building at 1/3 scale. This mock-up named VeRCoRs (VErification Réaliste du COnfinement des RéacteurS) was built near Paris, and is highly instrumented so that its behavior is monitored from the beginning of the construction. One of the main technical objectives of the project is to understand aging of buildings made of prestressed reinforced concrete and its effect on leak tightness evolution. Actually, at a 1/3 scale, the drying process will be nine times faster so that the studies of ageing can be speeded up. In order to verify this speed up, a numerical clone of VeRCoRs is developed at EDF to simulate ageing processes using EDF simulation tools (Salome-Meca, Code_Aster). This numerical model is also necessary to understand the ageing of the mock-up and to analyse on-measurable quantities such as stresses fields. Numerical results are compared to measurements carried out for now in terms of temperature, deformations and displacements. Finally, a first idea of VeRCoRs representativeness is drawn.