Calculation of chloride ion concentration in expressed pore solution of cement-based materials exposed to a chloride salt solution

Abstract

To investigate the relationship between the chloride ion concentration of the expressed pore solution (Ce) and the exposure solution (Ces) of cement-based materials exposed to a chloride salt solution, a calculation of the Ce, based on an electrical double layer (EDL) model was proposed. The Ce values were calculated using the proposed equations, applying the measured parameters: relative potential (δψ0), dielectric constant (ε), porosity (P), bulk density (D), volume percentage (pi) of pores with diameter di. The calculations explain why Ce does not always equal to Ces. The results indicate that the expression method does not test the concentration of free chloride ions in the bulk solution (CCl−b) or the average concentration of the transportable chloride ions (Cttr.a) in the pores. However, the ratio (Cr) of Ce to CCl−b and the relationship between Ce and Cttr.a can be calculated to more accurately measure chloride ion migration in cement-based materials.