Is it true that sea water should not be used in mixing concrete? We have heard conflicting reports.
Any water that contains chloride is potentially corrosive to reinforcing steel. The action on the steel is sometimes long delayed, and what may appear to be sound concrete may show signs of distress after many years. Corrosion of the steel causes expansion which disrupts the concrete. There appears to be no danger of corrosion of steel, however, if the concrete mixed with sea water is continuously immersed in sea water. There is also the possibility of sulfate attack and consequent deterioration by the use of sea water if the cement used has a high tricalcium aluminate (C3A) content. Many codes do not allow the use of sea water in concrete, though some do.