A mathematical model in charactering chloride diffusivity in unsaturated cementitious material
Yong Zhang (TU Delft - Materials and Environment)
Guang Ye (TU Delft - Materials and Environment)
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Abstract
In this paper, a new analytic model for predicting chloride diffusivity in unsaturated cementitious materials is developed based on conductivity theory and Nernst-Einstein equation. The model specifies that chloride diffusivity in unsaturated cementitious materials can be mathematically described as a function of chloride diffusivity in saturated state, water saturation and average pore diameter of the material. A series of experiments were conducted in order to validate the model. Mortar samples with varying cementitious mixtures were cast and cured for one year, followed by oven drying at 50 °C until desired water saturation levels (18 to 100 %) and homogeneous moisture distribution were obtained. The electrical conductivities of mortar specimens at various water saturations were measured and then converted into chloride diffusivities by using Nernst-Einstein equation. It is found that the experimental results can be well described by the analytic model proposed in this work.