Quantity will depend on the size of the barges to be built… The way it looks with seasteading, less is more.
LOL, of course. But I would propose a different approach.
For example, we now AS A FACT that ferrocement boats built in the 70’s are still navigating as we speak. That’s 48 years at sea. Not bad at all. And they could go for another 10, 20, 40,… It remains to be seen.
Therefore, a “ferrocement” (concrete built - for a lack of a better word) seastead built by 2020 WILL be around by 2070. That’s an excellent life span, for now…
The general consensus between the few of us still hanging around here is that the “best” material so far would be ferrocement (for “small” seasteading units, lets say up to around 100’-150’ LOA) or steel reinforced concrete (for larger than 150’ LOA units)
The process is already standard for such constructions, but studies have shown that adding basalt fiber to concrete will highly improve the overall quality (strengths) of the structure.
Now, regarding the basalt rebar. Personally, I wouldn’t recommend using it for building seasteads. Here is why.
Basalt is very light compared to steel. Basalt density 3000 kg/sq.m VS. 8000 kg/sq.m steel. That would make the basalt rebar built seastead way too light for it’s main application: people living permanently @ sea.
Seasteads should be built very heavy in order to provide the best stability (therefore the least degrees of motion) at any given seastate. Imagine that you start rolling 20-30 degrees on a light seastead in 10 foot seas, when “the norm” offshore is 20-25 foot seas. The quality of life on such seastead would suck even for seasoned sailors,…