To fulfil its numerous science objectives, the Gaia mission needs to account for the impact of the radiations at CCD level. Through the defects generated in the silicon, the radiations will not only degrade the overall signal-to-noise ratio of the measurements, but also corrupt them with a bias to be corrected on ground. In order to characterize this effect, and help deriving a proper calibration strategy, an extensive radiation test campaign has been carried out in EADS Astrium since 2006, covering the different instruments and CCD variants. We present an overview of this radiation test bench, and the different investigations performed so far and associated findings.