Concrete and Salt Water
Recently bought a cabin on the beach. Wanting to set some concrete anchors on the beach for a haul-out and a chain of logs break water. I welcome any advice on such a project, but I'm specifically wanting to hear from anyone with experience mixing concrete on the beach using beach sand and/or salt water. I've read in a couple of online resources that the salty sand and seawater only cause problems when re-bar is used, and there's (seemingly) no need for re-bar in an anchor. Does this sound right?
I don't have all the answers but I can tell you what I know.
The steel is for tensile strength and the concrete is for compressive strength in structural applications. Yours is more of a dunnage issue than a structural issue
Concrete cracks. The steel helps hold the chunks together.
The salt in the water will rust any steel placed within the concrete-coated steel might delay the inevitable.A couple of short, coated #3 rebars in your anchor should last well beyond your expectations.
The thing to remember about steel is that when it corrodes, it expands. Rebar inside concrete that begins to corrode will eventually expand and crack the concrete. There is rebar with various corrosion coatings available for use where corrosion is expected to be a problem. For your use, you probably can get away with out rebar but you will have to sink something in the concrete to attach whatever it is you are anchoring.
Like NRick said, you probably don't have to worry about needing rebar, but whatever you use as the "anchor" will be subject to the same corrosive forces that any rebar would have been exposed to, probably even more being that some of it will be exposed. In most construction projects where salt is a concern, they use things like epoxy coated rebar or stainless steel rebar to prevent the corrosion. Other steel used for things like light pole or rail anchors are typically hot-dipped galvanized. As long as you use something that is protected from corrosion, you should be okay.
I have had an ocean front cabin for a long time. Just get used to the fact that you have to look at them every few years. Even galvanized anchor chain doesn't last much past 2 years. If you are in Juneau there is a local outfit that makes a concrete mooring system, but if you aren't forget about buying and freighting one.