The greater point I'm getting at is whatever aggregate you use to make more concrete, making the concrete with Portland is still 8 percent of CO2 emissions. You can protect local environments and maintain concrete production, but what use is that when you're cooking the planet with the concrete in the first place? Gotta stop liberating the CO2 from rocks, not green wash it.

Uh, more than half of the earth's crust is made from silica.

How are we running out?

Coffee grounds are better used in compost. Less work and takes advantage of its actual content.

I'm all for reduction, but if you priced in the externalities even that would likely favor other materials in many applications that are extensively cement based. Including bitumen in some cases. I just think we have to be aggressively against cement usage because theres no stoichiometric way to get it to not be a massive source of carbon if we keep using it the way we do.

My problem with the don't throw the productive economy out by just trying to decarbonize argument is really structural though. It just gets to the point that we can't outgrow destroying the commons. Who cares if we maintain rapid development if the resulting assets are worthless?