Sorption in C-S-H at the molecular level: Disjoining pressures, effective interactions, hysteresis, and cavitation

Sorption processes are critical for drying and durability of cement-based materials. By means of molecular simulations, we study the behavior of C-S-H upon sorption according to various pore sizes at ambient temperature. For interlayer distances between 10 and 26 angstrom, we determine the sorption isotherms, confining pressures, energy profiles, equilibrium basal distances, and metastable domains during drying and rewetting, respectively. We quantify the pore-size dependency of water cavitation and sorption hysteresis in C-S-H. Cavitation in C-S-H is heterogeneous due to the presence of hydrophobic sites in an overall hydrophilic surface. The critical pore sizes for hysteresis disappearance and reversibility of capillary condensation are provided for C-S-H. We discuss the lower limit of validity of the Kelvin-Cohan description of adsorption and desorption in C-S-H.