Chloride binding isotherms determined for two different types of lime-based composite materials containing metakaolin are presented in this paper. The experiments are performed on small specimens with defined shape so that the effect of the porous structure is respected. Also, the experiment with crushed samples as in the original procedure by Tang and Nilsson is done for the sake of comparison and the differences analyzed. It is concluded that the chloride binding capacity of lime-based materials depends critically on the size of the sample.