The concrete won’t release the CO2 when it breaks down, since the quicklime in the cement reacts with CO2 to form limestone. The catch is that quicklime is mainly produced by heating limestone to release CO2, so making extra concrete won’t result in net carbon capture. But if the concrete was going to be produced anyway, I suppose it’s better to have it absorb the CO2 sooner rather than later.
The concrete won’t release the CO2 when it breaks down, since the quicklime in the cement reacts with CO2 to form limestone. The catch is that quicklime is mainly produced by heating limestone to release CO2, so making extra concrete won’t result in net carbon capture. But if the concrete was going to be produced anyway, I suppose it’s better to have it absorb the CO2 sooner rather than later.