Can cement be mixed with sea water instead of fresh water?
This is definitely not a good idea as there will be a reaction between the cement and the salt. Even though the cement will appear hard it will be weakened by the salt. There may however be special cements which are made to be mixed with sea water. Bill
Yes, but it changes the chemical properties of the cement.
The best practice is to use potable (fresh) water for a concrete mix design. If you are somehow left without another option the following information should help you make an informed decision. If the situation is regarding a structural portion of a home, business, bridge or otherwise important structure please seek a qualified engineer to help give you more specific information. If this is for a small project like a mailbox foundation or similar then I hope this information will be helpful in making a good choice. The answer depends on your steel reinforcing. If the concrete you are preparing the cement for will have steel reinforcing you will need to use corrosion resistant steel (such as stainless steel, MMX, epoxy coated, or galvanized) if you want to keep the steel from corroding prematurely due to the salt content of sea water. If you decide to use sea water in the mix and have steel anchor bolts embedded in the concrete, you will want to make sure that they are stainless steel or galvanized. Make sure that you use the same steel type (stainless or galvanized) for your bolts, washers, and nuts. Ultimately the saline properties of sea water will produce a harder concrete, but if that corrodes your steel your end result could be a dangerous failure. Your first choice should be to use fresh water in all but very special cases.
