It's probably not a new idea, but it might be newly-relevant seeing as concrete is under the magnifying glass for its emissions as it's curing. More expensive

It's probably not a new idea, but it might be newly-relevant seeing as concrete is under the magnifying glass for its emissions as it's curing. More expensive concrete might have become economically viable if it emits less greenhouse gas or if you need less of it. And if it's not currently economically viable it might still become viable in the future, prompting more research into it by companies hoping to have first-mover advantage. That said I'm not a concrete expert. I don't know why this sort of concrete isn't currently being used, nor the relative pricing of it relative to ordinary concrete.