I was the author of the SEI blog linked above, which was a summary of the CMU chapter of Building Structure and Global Climate. I’m happy to see that Angelus has added a simple calculator and especially pleased that it validates my earlier estimate that grout can triple the embodied content of a CMU wall.
Grout has a high embodied carbon content - higher than most concretes - because there is excess cement to balance the excess water needed to make the grout flow. This counteracts the efficiency of CMU manufacturing.
The embodied carbon of a CMU wall is the same as the same volume of concrete wall made of 3000 psi concrete. That’s what the Angelus calculator reports for a CMU a wall including grout, and comparing that to the median GWP from Climate Earth’s Concrete Selector tool. (https://selector.climateearth.com/).
The engineering wrinkle is you don’t need to fully grout a wall. At a minimum, only the cells than contain rebar need grout, which may be one quarter of the cells. For partitions and very light loads, they can remain ungrouted, Many engineers (either through laziness or inexperience) may specify more grout than is required. I was one of those over-specifiers in the past. So you could cut that impact by 1/3 for hollow partitions.
As for carbonation, in my research for the book showed that the benefits are small. CarbonCure technology, that uses carbonation during manufacturing has a very small improvement. For carbonation that occurs over the life of operation, in my opinion it is too little too late. The damage is done when the CO2 is put in the atmosphere during manufacturing (sunk cost), and we have no time to wait for the sequestration to occur to combat global warming. You need more surface area exposure for carbonation to make a dent.
The only take-away I learned about carbonation is demolished concrete can be ground up and used as fill. If left exposed to the air, the additional surface area can rapidly expedite the carbonation (which ends up decaying the concrete anyway).
I’m happy to discuss further.
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