A lot of controversial data are available in the domain of chloride binding in mortar and concrete.

Are the chloride physically bonded – adsorbed on the surface of the compounds of hardened cement paste?  Are the chloride bounded into compounds with the aluminates from cement?

The present paper try to present the work in adsorption tests of chloride onto mortar specimens completed with electronic microscopy images of contaminated samples.

Results of chloride fixation tests shows isotherms Freundlich like, specific to physical adsorption and suggests that chloride adsorption onto C-S-H is the main fixation process. The validity of adsorption tests was verified by comparing with the results of accelerated contamination of mortars test using migration of chloride under the action of an electric field.

SEM investigations didn’t showed any preferential sites for chloride fixation, as we expected in the case of chemical bounding.