Chloride-binders and their effect on the physico-mechanical properties of sulfate-resisting cement (SRC) hardened pastes upon exposure to sea water attack

In Egypt, the national strategic plan for population redistribution supports the establishment of new towns and urban settlements across the coastal zones to relieve the pressure on the packed Nile Valley and Delta and encourages internal migration to new urban coastal communities. Since reinforced concrete has a poor service record in these areas, this situation urged us to design a research program in which a new route has been followed for confronting the concomitant effect of sulfate and chloride attack. Therefore, sulfate-resisting cement (type V) has been used for preparing concrete. The cement has been blended with a chloride-binder for fixing free chloride into an insoluble (or poorly soluble) reaction product. As to the steel reinforcement, the research program will investigate steel protection by an innovative inhibited cement slurry coating. The current-first part-of the research program has been concentrated for determining the influence of a chloride-binder [lead oxide (PbO)] as well as a novel proposed chemical compound [lead nitrate: Pb(NO₃)₂], as chloride-binders, on the physico-mechanical properties of hardened SRC pastes upon exposure to sea water. The investigation disclosed that these compounds marginally delay the setting time relative to the chloride-binder-free pastes, yet they improve workability, maintain alkalinity (hence carbonation resistance), and yield better compressive strength.