PREDICTION OF LONG-TERM CHLORIDE CONCENTRATION IN CONCRETE

The paper presents a wide range of experimental data of the authors and of other researchers on acid-soluble chloride diffusion in different mixes of concrete, and shows conclusively that the chloride diffusion coefficient D(c) is strongly dependent on the period of exposure of concrete to a chloride environment. Consequently, long term prediction of chloride concentrations on the basis of Fick's second law of diffusion, which inherently assumes a constant value of D(c), is not an accurate procedure. A differential equation is derived based on the above law of diffusion, which takes into account the time variation of D(c), and a procedure is outlined for the accurate prediction of long term chloride concentrations in concrete. The chloride concentration profiles derived using this procedure show good correlation with experimental data.