Mechanical and time-dependent behavior of seawater concrete under different curing conditions

The increasing scarcity of freshwater, intensified by climate change, pollution, and rapid urbanization, demands for sustainable alternatives in the construction industry, such as the use of seawater for concrete production. In this framework, this study addresses the investigation of compressive and tensile behaviors, and shrinkage and creep responses, of concrete produced with seawater and freshwater over time, while submitted to different curing conditions. Additionally, the study assesses the accuracy of existing analytical models that correlate concrete compressive strength with other mechanical properties, and existing formulations for modeling shrinkage and creep strains over time. The quasi-static properties of seawater concrete (SWC) and freshwater concrete (FWC) were analyzed after 28 days of air curing and during 2.5 years of seawater immersion at room temperature (RT, ~ 23 °C), 40 °C, and 60 °C. Shrinkage and creep deformations were assessed using specimens tested under constant temperature of 20 °C and relative humidity of 60%. The results showed that the use of seawater slightly reduced mechanical performance at an early age (up to 15% for compressive strength and 34% for tensile strength), with differences diminishing over time. Regarding shrinkage and creep, SWC exhibited reduced shrinkage but experienced higher creep strains than FWC. Furthermore, the ACI formulations demonstrated adequate accuracy in predicting shrinkage for both SWC and FWC compositions. These findings suggest that seawater can be used as mixing water in concrete without long-term detrimental effects. Therefore, seawater-mixed concrete may represent a feasible and resource-conscious alternative for construction in coastal and marine environments.