Modeling the chloride concentration profile in migration test based on general Poisson Nernst Planck equations and pore structure hypothesis

The rapid chloride migration test is widely used in estimating the diffusivity of cement-based material. However, the concentration profile predicted in the conventional method was found different from the realistic one. In this paper, the current models attempting to describe the concentration profile are introduced. Experimental test is carried out to found the realistic concentration profile. A system of general Poisson–Nernst–Planck (PNP) equations is formed by considering the influence of electrophoreses, relaxation, etc. A new model is built up based on the general PNP equations and a hypothesis of pore structure to explain the realistic concentration profile. A semi-empirical model is simplified from the new model according to the experimental evidence. And the semi-empirical model is applied to analyze the influence of source concentration on the chloride penetrability.

► The realistic chloride concentration profiles on various test conditions were determined.
► A general PNP model considering the influence of electrophoreses, relaxation, etc. was established.
► A hypothesis of pore structure was assumed to explain the realistic profile.
► A semi-empirical model was simplified to calculate the diffusion coefficient.
► The influence of source concentration on migration test was analyzed.