Effect of bound chloride on extraction of water soluble chloride in cement-based materials exposed to a chloride salt solution

In this study, chloride ion concentration in the water extracted solution was measured. For comparison, it was also calculated based on the electrical double layer model under extraction equilibrium. The results indicated that the release of physically bound chloride can result in 1-7 times higher water extracted chloride ion concentration than free chloride ion concentration. With increase of fineness of powder, the chloride ion concentration in the water extracted solution increased. When powder fineness was higher than 1 µm, a very small amount of water could completely extract the water soluble chloride under extraction equilibrium. With increase of water/solid ratio and water temperature, release of chemically bound chloride led to a higher concentration of chloride ions in water extracted solution. The calculation is very helpful for discussing the effects of physically and chemically bound chlorides on extraction of water soluble chloride. Finally, suggestions for improvement of water extraction method were proposed by taking into account the experimental parameters influencing the release of bound chloride.