This paper is aimed to evaluate the influence of marine sediments and shell powders on the chloride penetration through composite cement materials. The sediments have high water and chloride contents and calcite, quartz, illite and kaolinite as principal minerals. The shell powders are entirely composed of calcium carbonate and traces of other impurities. Four mixtures of treated sediments and shell powders at 650 and 850 degrees C are added to Portland cement at 8, 16 and 33% by weight. Substituted pastes and mortars are tested at different chloride exposure conditions. It is shown that the partial cement replacement of CEM I with sediments and shell powders can decrease the corrosion risk of the reinforcing steel of concrete by changing the microstructure of the material due to the compacting effect and extending more ions to react with chlorides. Hence, the free chlorides in the pore solution were reduced.