Concrete samples from inside and outside the structure showed strikingly different levels of calcium carbonate, which was rapidly being formed inside the domes

Concrete samples from inside and outside the structure showed strikingly different levels of calcium carbonate, which was rapidly being formed inside the domes as huge amounts of carbon dioxide reacted with calcium hydroxide in the concrete. ... Severinghaus said of the calcium carbonate. "It's 10 times more than outside." From https://www.nytimes.com/1993/10/05/science/too-rich-a-soil-scientists-find-the-flaw-that-undid-the-biosphere.html https://www.nytimes.com/1993/10/05/science/too-rich-a-soil-s...