A review of porosity and Diffusion in Bentonite (pdf) (2.4 MB) - Posiva

9Figure 3. (A): Anion-accessible porosity in bentonite packed at different dry density asa function of NaCl concentration in the external solution, and (B, C, D): modeldistributionof water over Cl - -accessible (assumed equal to ε free ), DDL- (ε DDL ) and interlayer(ε IL ) porosities for packings of (B) 1280, (C) 1580, (D) 1700 kg/m 3 . Experimentaldata from Muurinen (2006).The optimized values of the parameters a 0_IL , a osm and a DDL are listed in Table 1. Thenumbers express the different trends in the two datasets. In Van Loon’s experiments, theCl - -accessible porosity is dominated by the change of the interlayer porosity (relativelylarge numbers for a 0_IL and a osm ), whereas the DDL porosity is influential only whenionic strength decreases below 0.05. Muurinen’s data show equal importance of bothporosity types, although also here, the DDL-porosity becomes predominant when theionic strength becomes less than 0.1.The numbers permit calculation of the specific external and internal surface area of themontmorillonite. The external surface area is:Aext3.09 1010afDDLDDLwmmdryIt was assumed that f DDL = 1, and w mm = 0.8 and 0.71 for Muurinen and Van Loon’s data,respectively.(12)