Since cementitious materials used in repositories will be in contact with water, one of the most important tasks is to assess their long-term performance while they are being degraded very slowly by leaching. The authors have proposed an electrochemical acceleration test method and clarified its applicability. In this method, a specimen is placed between two glass vessels containing water. An anode and a cathode connected to a DC power source provide a potential gradient across the specimen. Ca2+ ions in the pore solution move rapidly to the cathode side, and thus hasten cement hydrate dissolution.
In this study, we obtained two types of almost homogeneously degraded specimens by controlling cumulative quantity of dissolved Ca2+ ions. In the first type, there was no Ca(OH)2and the C-S-H phases underwent insignificant alteration, whereas in the second type, degradation of the C-S-H phases occurred.
As a preliminary evaluation of cementitious materials, diffusion coefficients of tritiated water were measured for nondegraded and degraded specimens. Diffusion coefficients were increased by degradation and closely corresponded to changes in porosity.