Leaching model for a cement mortar exposed to intermittent wetting and drying



Numerical simulations of inorganic species release from an intermittently wetted cement material without carbonation effects are presented. The intermittent mass-transport (IMT) model combines previously developed approaches describing constituent diffusion coupled with solid-phase dissolution/precipitation and two-regime drying of a cement matrix stored at constant relative humidity. Model simulations were validated using experimental data showing the effects of intermittent wetting on release of major matrix species (Ca, Na, K, Cl, OH) and pH-dependent trace metals (Cd, Pb). The IMT model successfully describes constituent release flux for intermittent wetting cases with storage in an inert atmosphere (100% N2) at three levels of relative humidity (23%, 48%, 98% RH). Leachate pH simulation accounted for the release of soluble alkaline salts in conjunction with the dissolution of calcium hydroxide. The release simulations for pH-dependent species were subsequently improved over pH determination based solely on calcium hydroxide dissolution.