Dependence of water diffusion on water to cement ratio in ordinary portland cement pastes

Takiya, Hiroaki*; Tanaka, Shingo*; Noda, Natsuko*; Sato, Seichi*; Kozaki, Tamotsu*; Sato, Haruo; Hatanaka, Koichiro

It is important to clarify the behaviour of cement porewater for performance assessment of radioactive waste disposal. In this study, we measured apparent self-diffusion coefficients of water in Ordinary Portland Cement pastes with various water-cement ratios (W/C) as the part. The diffusion experiments were carried out as a function of W/C ratio in a range of 0.4-0.8, and O-18 was used as a tracer of water. The apparent diffusion coefficient increased with W/C. All penetration profiles of O-18 showed a tendency to shift from simple diffusion profile with increasing diffusion depth. It was indicated existence of some different diffusion pathways.