Abstract
High strength and ultra low permeability concrete (HSULPC) is thought to be an alternative material for a radioactive waste package containing transuranic radionuclides (TRU wastes) for geological disposal. Thus high confining ability is required for HSULPC. In addition, knowledge of time-dependent fracturing and change of permeability due to fracturing is important. For cementitious materials, self sealing of fracture due to the precipitation of calcium compounds can occur in water. This can affect long-term stability and decrease of permeability. In this study, the sealing behavior of macro-fractured HSULPC in water was investigated using micro-focus X-ray CT and image analyses. It was shown that the sealing of fracture by precipitation occurred only near the edge of the specimen. Using the technique of image registration and image subtraction considering the gap between X-ray CT images, the sealed regions in fracture were extracted successfully. The percentage of sealed volume in fracture increased with elapsed time. It is concluded that high confining ability of HSULPC can be maintained due to the self sealing even if fractures are included.
