In 2014, David South, the inventor and patent holder for Ecoshell dome construction, wrote the following on the Monolithic Dome Institute website.

Salt Water Concrete—A Reality David B. South • Published on Feb 25, 2014 • The President’s Sphere

Over the years, I have received numerous calls asking about the feasibility of building Ecoshell I Domes along thec oasts of islands throughout the world. It is common knowledge that using salt water, sea water or salty sand isn ot a possibility when building concrete structures.

The problem with using anything salty doesn’t lie with the concrete; the problem is with steel reinforcing. The minute steel reinforcing comes in contact with salt water, it begins to rust. As steel rusts, it expands and breaks up the surrounding concrete. This is not new knowledge, it is a simple fact that this will happen every time.

Here is the question: “What if we don’t use steel reinforcing, but instead, use basalt reinforcing?” Basalt is the technical name for lava rock and as we all know, lava rock does not disintegrate in salt water. Lava rock (Basalt) rebar is becoming more popular because it is twice as strong as steel rebar, it won’t rust and it is much lighter.

Basalt reinforcing is made like fiberglass. First, the base materials are heated to the melting point, then pulled or pushed through a die into fibers smaller than a human hair. The fibers are then bonded together with epoxy to make the basalt rebar. The fiberization process was invented in Russia. Basalt reinforcing is being manufactured in Russia, Ukraine, China and other places.

Upon learning of basalt reinforcing, I contacted my number one engineer, Dr. Arnold Wilson, who spent the last fifty years teaching and researching thin-shells and concrete dome buildings. He reported that he could see no problems with using basalt reinforcing with concrete made with sea water and beach sand.

Obviously, there are other problems as beach sand is often pretty fine in some areas and in other areas it would make good aggregate. But, nevertheless, the question has been, “Can we do it?” The answer is, “YES!”

Last week, I called Steven H. Kosmatka, Vice-President of Research and Technical Services for the Portland Cement Association. We had a conversation regarding building the Ecoshell I Domes using salt water, beach sand and basalt reinforcing. I explained to him that we were not looking for terribly strong cement or concrete—in most cases, we need only 250 psi concrete. (Our normal concrete mix is 4,000 to 5,000 psi.) Steven agreed with me that for the Ecoshell buildings there should be no problem, whatsoever, building long-term or permanent structures using beach sand and Portland Cement. The whole key is to use the basalt reinforcing. You simply order the basalt reinforcing and install it.

Think of what a cost-savings this would mean in terms of building along the coasts of millions of islands around the world! It is just a matter of gathering up the beach sand, using the salt water to mix the Portland Cement and constructing the Ecoshell I.

One consideration during the construction process is the fact that salt water tends to speed up the setting of the concrete. However, adding 20 percent fly ash will slow the setting and help make the concrete even more effective. Also, the Portland Cement needs to contain lower or less sulfates when used with the salt water. This type of cement is readily available.

So what I am saying is this: Use the salt water and beach sand. Use Portland Cement mixed with 10, 15 or 20 percent fly ash. The major requirement is: Use Basalt reinforcement and not steel reinforcement. You can build anything you want and expect it to last centuries, just the same as conventional.

Our Monolithic website has a tremendous amount of information about how to use the basalt reinforcing, mix the concrete and how to get the job done.

Thank you and let’s get after it!

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(Webpage Author notes follow)

Now in 2024, after much more research, the following is true.

If the domes are not in constant immersion in seawater, Type V (Sulfate Resistant) cement is not needed. PPC (Portland Pozzolana Cement) with fly ash content of 30% is roughly comparable to Type V cement in its resistance to Sulfates and is preferred for its cost and smaller carbon footprint.

Basalt is now manufactured in North America, China. Russia, Romania, Japan and other countries. Its costs are comparable or less than steel rods of the same diameter, and obviously much simpler to handle while having 2.5 times the tensile strength and 450% less weight than same diameter steel rods.