An approach of NMR relaxometry for understanding water in saturated compacted bentonite

1H NMR relaxometry is applied for investigation of water state in compacted saturated bentonites (Kunipia-F, Kunigel-V1 and Kunigel-V1/sand mixture). The dry density is varied from 0.4 to 2.0 g/cm3. The analyses of the magnetization decay to obtain relaxation time constants were implemented by two kinds of methods: discrete and continuous relaxation time distribution, as multi-exponential models.Assuming the relaxation time with 3-hydrated layer which is used as a threshold whether bulk-like water (pore water), the proportion of bulk-like water to total water were evaluated. The proportion of bulk-like water obtained from continuous distribution analysis of relaxation time were well in agreement with XRD results in the past.The knowledge of water state related to the dry density was given that bulk-like water was disappeared in compacted saturated Kunipia-F at high dry density (>1.2 g/cm3), on the contrary bulk-like water of about 10% remained in Kunigel-V1 and Kunigel-V1/sand mixture regardless of high dry density (>1.6 g/cm3).