Structural Analysis Sample Clauses

Structural Analysis. The H2O and CO2 density profiles along the direction perpendicular to the pore surface in C-S-H pores show oscillations, which are typical of fluids in nano-confinement (Figure 3). For C/S = 0.83, the density profiles for both 1-nm and 2-nm pores (Figures 3a and 3d) show that CO2 molecules lie within the first hydration layer of the surface; coexisting with water molecules. The density peak on the left of the surface is attributed to the H2O/CO2 molecules trapped within the channels formed by the silicate chains running along the [010] crystallographic direction. In contrast, for higher C/S ratios (1.5 and 1.75), the CO2 molecules are located far off from the surface with H2O molecules forming a definite hydration layer adjacent to the C-S-H surface. As the pore size increases from 1 to 2 nm, bulk-like density profile for the water molecules is attained above approximately 7 Å from the surface, which is typical of other slit-like mineral nanopores (e.g., Xxxxxxxxxxx et al., 2015). However, there is a noticeable depletion of CO2 concentration near the C-S-H surface, especially at higher C/S ratios, since the surface is becoming relatively more hydrophilic. This observation is consistent with recent simulations results for competitive adsorption of H2O/CO2 mixtures into similar smectite clay interlayers, which also show some CO2 depletion at the surface with a more hydrophilic local environment (Xxxxxxxxxx et a., 2018b). Figure 3: Atomic density profiles of H2O and CO2 mixtures within the nanopores of C-S-H models. a) 1-nm pore at C/S=0.83; b) 1-nm pore at C/S=1.5; c) 1-nm pore at C/S=1.75;