Possibility of Usage of Seawater for Mixing and Curing of Concrete in Salty Water Localities

Aims: This study examines the possibility of using seawater as an alternative to freshwater in concrete mixing and curing in areas prone to saltwater. The study was as a result of shortage and scarcity of Freshwater in some parts of the world; mostly in the coastal areas, where seawater is the only source of water.

Place and Duration of Study: Seawater was obtained from Port Harcourt Tourist beach, River State, Nigeria was used to mix and cure a set of concrete cubes (CSW). And freshwater obtained from our Civil Engineering laboratory was used to mix and cure another set of concrete cubes (CFW) that serves as a control. The maximum days of curing were 28days.

Methodology: Concrete cubes of 150x150x150mm3 were produced and cured with sea and freshwater respectively. The compressive strength of those cubes were determined using Compression Testing Machine. The studied variable was only water used for mixing and curing of the concrete cubes. Other constituents of the concrete: cement, fine aggregate, and coarse aggregate were kept constant.

Results: It was found that the compressive strengths of concrete cubes mixed and cured with seawater at 7, 14, 21 and 28days were within the acceptable limits and a bit higher than those of cubes mixed and cured with fresh water. The variation in compressive strength of CSW and CFW at the 28th day of curing was just 1.45%. Hence, the seawater didn’t affect the compressive strength.

Conclusion: With the little variation in compressive strength between the CSW and CFW at the 28th day of curing; it is recommended that seawater can possibly be used for concrete mixing and curing in areas where freshwater is not available; provided that the concrete is kept inherently dry to prevent corrosion. In addition, higher concrete covers can be provided when designing the concrete structures. Meanwhile, careful and adequate design, well-supervised construction, and curing should be ensured to improve the ingress resistance of the concrete structures. However, the long-term effect of the seawater on the properties of concrete and reinforcements were not investigated.