Dynamic determination of sorption isotherm of cement based materials

A dynamic method of determining sorption isotherm is proposed. Changes in humidity boundary conditions were applied to specimens of hardened cement paste having various water–cement ratios, as well as to autoclaved aerated concrete, and water adsorption rates were continuously recorded in a sufficiently short period. The diffusion equation was analytically solved and was fitted to the adsorption rates resulting in the rapid estimation of equilibrium moisture content. Results of equilibrium moisture content, the primary data of moisture capacity, showed good agreement with literature values. The adsorption rate measurement took 8 h for autoclaved aerated concrete and 12 h for hardened cement paste with a measurement interval of 60 s to predict an equilibrium moisture content at an ambient relative humidity.