It's concrete, not cement. Cement is a component, not the end product.

If you leave a bag of portland cement outside and let the rain cures it then that's a cement block.

And the article mentions both but in contradicting contexts. Is "cement blocks" actually "concrete blocks"? Then later it mentions cement being incorporated into the resulting concrete, so what was the previously mentioned "cement blocks"? Nothing made of cement in the shape of blocks are ever incorporated into concrete. Cement powder is.

Anyway, cool concept. In the mean time, the world also needs to figure out how to make concrete more green, because manufacturing cement releases a lot of greenhouse gases.