Hello CLF Team - What is the lowest embodied carbon CMU block available in SoCal with and without a cost premium? Thank you, Aaron
Expanding on Aaron’s question, we did a little preliminary research on CMU that might be helpful.
We’re working on a few projects likely to use CMU as the façade and vertical structure. Initially, we wanted to source lightweight block due to the improved thermal performance, but decided to compare the embodied carbon numbers of LW block against MW and NW block. Digging into the EPDs—primarily from Angelus Block’s website and EC3—we found lightweight CMU tends to have at least as much cement as a percentage of the overall mix to achieve the same compressive strength as medium and normal weight CMU. (This makes intuitive sense. Manufacturing process and volume of cement are determinant factors in strength, density is not.)
A few important caveats:
- The EPDs we looked at exclusively account for the A1-A3 product stages.
- Without a wholistic LCA it’s hard to assess if the additional cement in the block is offset by smaller foundations/footings (resulting from the lower structural weight), reduced rigid insulation in the walls, less fuel freighting the CMU to the project site, etc.
Hey @aaron.vaden-youmans! Do you intend to use for structural application or for non-structural partition walls?
For non-structural application, you might have some more flexibility. There’s a company that USGBC-LA was supporting that takes plastic waste and makes into blocks. There’s also an interesting living lab in Seattle by @ddavies (way to go Don!) that uses Prometheus blocks, but that’s pretty early stages and likely not available for commercial use today.
For structural blocks, here are a few you might track for having appropriate ASTM test data and see where they’re at with manufacuring and distribution. Carbon Built started out of UCLA research, but last I heard their plant was starting in Alabama. Perhaps others have more recent information…
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Thank you Luke! These links are great.
I’ve looked into all and waiting to hear back on the regional availability of Prometheus and Biomason blocks. Indeed, it seems CarbonBuilt is not available in our region yet.
We need these for exterior structural application in Southern California (for new rail stations).
At this point, we think our best bet is the Angelus’ CarbonKind block.
Let us know if we are missing anything in terms of innovative low-embodied carbon CMU in SoCal.
Tracking this thread!
In the past, best I’ve been able to do is pointing to the best-in-class available CMU blocks/suppliers. The Angelus CarbonKind block being a leading product we have recommended in the past.
All others seem to be in early testing stages and not yet commercially available, at least last time I reached out. @aaron.vaden-youmans in the case you hear back from Prometheus and Biomason, would you mind sharing your conclusions here?
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We have heard back from CarbonBuilt. They are currently working on expanding out West and should have product availability out of their Flagstaff producer partner’s plant towards the end of the year. Also, they have partnered with Climate Earth for their EPDs and will have a preliminary EPD ready once they have finalized their mix design and a final EPD after 12 months of data collection at the plant.
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Semi related question, has anyone updated their project documents (ie specifications), CMU division, to include language about low-embodied carbon CMU; similar to what you could do for cast-in-place concrete division 03?
We are wanting to update our specifications but struggling a bit on how to exactly since CMU is made up of both the concrete block itself, where we could use a performance spec similar to CIP concrete, and then the grout portion - which we know little about in terms of laying out GWP limits.
Any thoughts on how to actually incorporate low embodied carbon CMU on a project would be appreciated!
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Think this is a really great point! And actually maybe somewhere perhaps significant impact could be made with relatively little effort (if everyone changed). At least in my design experience (all on larger steel / concrete buildings), the CMU was a an oversight mainly delegated to typical details. A lot of walls potentially being fully grouted out of conservatism…
Doesn’t look like there is enough data for CLF to establish baselines for CMU or grout. Would be great to get some SE 2050 guidance on this–and I think it’s potentially in the works! @mdwebster
I have reached out to someone from CMHA (concrete masonry and hardscape association) inquiring about when they expect to publish an industry average EPD and this is what they said in Feb 2024:
"We expect to publish the CMHA Industry Average EPD during the first half of this year. I would not recommend using the NRMCA’s industry averages for CMU block because Ready Mix and Dry-Cast Manufactured Concrete Products like CMU are significantly different in both mix design and manufacturing process. Using the CCMPA data is a reasonable approach with the caveat that there is no guarantee that the range of mix designs in the CCMPA industry average are that same as across the US or that CMU meeting the CCMPA industry average are available in all regions of the US. "
When I reached out to The Masonry Society the directed me to an IW-EPD for clay brick; which isn’t necessarily the same for our structural purposes of CMU. There is also manufacturer specific ones from Basalite and Angelus Block (out of California), but again - not industry wide.
If I get an information I will make sure to post it here.
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The SE 2050 Specifications Guidance offers a few suggestions for specifying CMU:
- Specify grout using strength method instead of prescriptive method.
- SCMs for block/mortar/grout.
- Carbon mineralization.
- GWP limits on rebar.
We’re also working on some design (vs. procurement/specs) guidance which will be published soon.
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See this older post: Concrete Masonry Units (CMU) - #9 by heyslivers
especially about the grout. Some ready-mix concrete suppliers can provide grout mixes made to TMS performance specifications.
Large projects need a lot of grout, so they come from concrete plants supported with compression test data. Ask local suppliers if they can use SCMs or Type 1L.
Incentivize bidders on that light rail project by requiring them to report embodied carbon as part of their bid. See @mark.chen talk about this here and at minute 12 of his more recent presentation here courtesy of CLF Seattle.
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@JLee_SF, updating project specifications to include low-embodied carbon CMU can indeed be challenging, especially considering the dual nature of CMU and grout. To address this, you might start by adopting performance-based specifications for both the block and the grout, similar to approaches used in cast-in-place concrete. Additionally, incorporating guidelines from the upcoming CMHA Industry Average EPD and SE 2050 Specifications Guidance could provide a more standardized approach. Engaging with local suppliers for tailored advice and encouraging bidders to report embodied carbon can also drive better outcomes.