Studies on water and nitrogen adsorption on hardened cement pastes. II-Thermodynamics of adsorption

Heats as well as entropies of water and nitrogen adsorption on hardened cement pastes of various pore structures were computed. Water vapor adsorption is accompanied by a decrease in integral entropy relative to the liquid state, while nitrogen adsorption is accompanied by an increase in integral entropy. The results could be related to the pore structures of the various pastes. For water adsorption, the molecules seem to be oriented in a definite array with more order than the liquid structure, and depending on the pore size, the normal liquid structure is resumed at some distance far from the surface. Nitrogen results could be described in terms of the inaccessibility and exclusion of the molecules from parts of the pore system.