Prediction of chloride ingress and binding in cement paste

摘要: This paper summarizes recent work on an analytical model for predicting the ingress rate of chlorides in cement-based materials. An integral part this is a thermodynamic phase equilibria hydrated Portland cement. The model’s ability to predict chloride binding cement pastes at any content chloride, alkalis, sulfates and carbonate was verified experimentally found be equally valid when applied other data literature. introduced into existing Finite Difference Model concrete which takes account its multi-component nature. “composite theory” then used diffusivity each ion based assemblage present paste. Agreement between profiles Cl/Ca ratio predicted by those determined 0.45 water/powder exposed 650 mM NaCl 70 days. confirms assumption essentially instantaneous where quasi-equilibrium established locally. does not imply steady state diffusion however. It simply implies that incremental increases concentration diffusing ions pore solution will rapidly re-equilibrate with hydrates locally, where, greater bound free ions, buffering effect slows down ingress. In case chlorides, greatest high contents AFm (AFm aluminium ferrite compounds single (mono) formula unit CaX.) low alkali metal contents.