Can seawater be used as mixing water for durable and sustainable RC structures?

Nowadays the use of chloride-contaminated raw materials is prohibited for reinforced concrete (RC) structures. Beside possible effects on the early stages of cement hydration and the long-term development of strength, the primary reason is corrosion of black steel reinforcement. In fact, it is well known that chlorides, destroying the passivation film, make steel susceptible to pitting corrosion. Thus, design standards worldwide aim at limiting the use of chloride-contaminated materials. However, the use of chloride-contaminated raw materials for the production of concrete would be advantageous since it would allow saving natural resources, such as fresh water, leading to enhanced environmental sustainability. In the framework of a research project financed by the Infravation Program (Advanced systems, materials and techniques for next generation infrastructure), an experimental study is undertaken aiming at demonstrating the safe utilization of seawater and salt-contaminated aggregates (natural or recycled) for a sustainable concrete production when combined with non-corrosive reinforcement to construct durable and economical concrete infrastructures. This paper focuses on a preliminary evaluation of the possibility of replacing fresh water with seawater when combined with different types of stainless steel reinforcement. Through a performance-based approach, RC elements made with fresh water and seawater, different constituents and stainless steel bars were simulated under exposure to different marine environments to define possible materials combinations able to guarantee a target design service life.