4 ms·
I’ve also read that concrete absorbs CO2, in significant enough quantities that an isolated ecosystem experiment had to be aborted because plants weren’t gettin
by h4b4n3r0 8y ago
I’ve also read that concrete absorbs CO2, in significant enough quantities that an isolated ecosystem experiment had to be aborted because plants weren’t getting enough of it.
- MauranKilom 8y agoI'm not doubting it, but on the other hand I don't think that the cement will re-absorb a significant amount of its own mass in CO2 (which it would have to in order to offset this 1-to-1 CO2 footprint).
- schiffern 8y agoPortland cement is at least 80% CaO, so in theory it's 63% of the cement's dry mass (CaO + CO2 -> CaCO3)[1]. In practice it's ~43% that value, or 27% of the cement's dry mass.[2] [1] https://en.wikipedia.org/wiki/Cement_kiln#Carbon_dioxide https://en.wikipedia.org/wiki/Cement_kiln#Carbon_dioxide [2] https://www.nature.com/articles/ngeo2840 https://www.nature.com/articles/ngeo2840
- MauranKilom 8y agoSo apparently it depends on the type of cement - non-hydraulic cement hardens as you described, while hydraulic cement does not absorb CO2 but instead hardens in the presence of water. I guess they wouldn't have a reason to use hydraulic cement for this though, so it seems you're right.
- schiffern 8y agoIt's true that hydraulic cements (eg Portland cement) harden by a different mechanism, but they too will fully carbonatate over time. https://www.astm.org/DIGITAL_LIBRARY/STP/PAGES/STP39460S.htm https://www.astm.org/DIGITAL_LIBRARY/STP/PAGES/STP39460S.htm https://nvlpubs.nist.gov/nistpubs/jres/60/jresv60n5p441_A1b.pdf https://nvlpubs.nist.gov/nistpubs/jres/60/jresv60n5p441_A1b.... https://en.wikipedia.org/wiki/Carbonatation https://en.wikipedia.org/wiki/Carbonatation