[raverbashing]

Read the page of the company doing it, that's not exactly what they're doing (which you correctly point out it would be pointless) - http://www.blueplanet-ltd.com/

[innocentfelon]

I read it again, twice. That is exactly what they’re doing.

Their starting material is CO2-source cement, not some natural “rock”.

Counterexamples are substantially more helpful than downvotes.

[raverbashing]

It seems they're not replacing the quicklime, but the gravel. The left column is confusing, the right column is better.

> A rock particle is coated with our synthetic limestone, forming a carbon-sequestering coating that is 44% by mass CO2.

That's where the CO2 goes, not in curing the CaO

[08-15]

But where does the Ca come from? Obviously not from limestone...