Unsaturated ion diffusion in cementitious materials – The effect of slag and silica fume

Abstract

This paper investigates the moisture dependency of ion diffusion in binary cementitious binders with Portland cement (OPC) in combination with slag or silica fume. Resistivity measurements and calculations with a thermodynamic model, GEMS, were used to assess the unsaturated chloride diffusion coefficient. The results show that the relation between the relative diffusion coefficient and the degree of saturation is not significantly affected by w/b (in the investigated range of w/b from 0.38 to 0.53), while the investigated binder compositions seem to affect the relation. These results are of value for service-life models, where they potentially represent important input data. The results also highlight the need for considering the pore solution conductivity when using resistivity measurements for evaluation of ion transport properties.