Sea water leads to a zoned phase changes at the surface of concrete. The surface is often covered with a crust consisting of brucite and calcite. Followed by a leached zone poor in chlorine, sulphur, and calcium where one potentially can find M-S-H. In the following zone one can find sulphur enrichment and the chlorine and calcium content starts to increases. Deeper in the chlorine content reaches a maximum and then gradually decreases again moving even deeper into the concrete. These changes in the phase assemblage at a sea water exposed concrete surface seem to be independent of the tested cement compositions (up to 30-50 % replacement with fly ash or slag). Whether this also indicates a limited difference on biological growth on these surfaces remains a question.