New Accelerated Leaching Experiment: The LIFT Procedure

In the past decades, cement-based materials have been increasingly used for the construction of radioactive-waste barriers. The design of durable structures for this specific application requires a precise knowledge of the evolution of the material engineering properties over a 1000-year period. Among the wide range of degradation phenomena to which the structure can be exposed during its service life, the leaching of calcium appears to be the most critical. Given the intricate nature of the leaching process, a reliable prediction of the long term behavior of the concrete barriers can only be made through numerical modeling. In order to generate more quantitative information on the subject, a new accelerated leaching test has been developed. The operating principle of the test is quite simple. The leaching process is accelerated by applying an external electric field through the material. This paper details the different electrochemical phenomena involved during a LIFT experiment. It also presents experimental data obtained for various neat paste samples. In this series of tests, the evolution of the hydrated cement paste microstructure was studied using various experimental techniques, such as X-ray diffraction, DTA/TG analyses and scanning electron microscopy. The advantages and limitations of this new procedure are discussed.