Concrete is something like a tenth of humanity's total CO2 emissions, so if this is something that lets us use less concrete then that's actually great
The process of making it involves cooking limestone until the carbon dioxide comes out, basically. Limestone is CaCO3 (one calcium, one carbon, three oxygen). Cement requires lime, which is CaO (one calcium, one oxygen). That leaves a C and two O, which stick together on the way out