Thanks for the explanation, those are good points. Though wouldn't the interior concrete not harden if it wasn't able to absorb CO2, since my understanding is t

Thanks for the explanation, those are good points. Though wouldn't the interior concrete not harden if it wasn't able to absorb CO2, since my understanding is that's fundamental to the hardening process? And agreed that surface area would effect the rate of absorption. I understand it can take hundreds of years for concrete to fully harden, which I could see being effected surface area and ability of the material to breath.