MIXING CONDITIONS IN APPLICATION OF BENTONITE GROUTING TO RADIOACTIVE WASTE DISPOSAL

The purpose of this study was to understand the flow properties and permeability of bentonite grout with NaCl added, using laboratory tests, and to clarify the mixing conditions of bentonite as a material. Given that the required permeability of clay grout is 10 − 9 (m/s), the combination of grout (W/B) becomes 6 or less. The viscosity of the grout was measured, and because the viscosity was higher than the thickest cement milk on dam grouting, it was found that grout with a W/B of less than 10 was difficult to inject into rock joints. We then added NaCl to grout with a W/B is 6, and its viscosity decreased as the amount of NaCl increased. A grout of viscosity able to be injected into rock joints was achieved by adding NaCl in a density higher than ”W: NaCl = 40:1”. Next, the permeability of a bentonite suspension with NaCl was examined using the falling head permeability test. Testing the sample ”B:W:NaCl = 20:20:1” for 10 days revealed that the initial permeability 10 − 8 (m/s) decreased to 10 − 10 〜 10 − 11 (m/s). These results showed that a suspension to inject into rock joints could be made by adding NaCl, and clarified that permeation of groundwater into the suspension causes a decline in permeability.