CarbonKind™
Low Carbon CMU
Concrete masonry units (CMU) are made of cement and aggregates, which make them officially a concrete. However, they are not that type of concrete; they contain a considerably lower percentage of cement than poured-in-place (PIP), or wet-cast concrete. Up to two-thirds less.
"Not all concrete is created equal.
CMU contains far less cement than other types of concrete and therefore, less CO2 impact."
Of course, in a concrete masonry wall CMU are typically paired with masonry grout, also a concrete, but a very specific kind of concrete. It is a natural candidate for high amounts of supplementary cementitious materials (SCM) which are used to replace cement. (See links below in There’s More to Concrete Masonry for more information.) These characteristics already make concrete masonry a desirable choice.
It’s even better now.
CarbonKind
Angelus Block has taken a great system further with CarbonKind, a CMU with substantially lower CO2. CarbonKind does not use higher-impact ordinary Portland cement (OPC), but instead, incorporates a blended cement, Portland-limestone cement, or PLC.
PLC is getting increased attention as an alternative to OPC. By reducing a portion of limestone in kiln-fired clinker, then adding it post-kiln, PLC reduces energy input and minimizes the CO2 released by its production. It is notable Angelus Block began using PLC before it became popular in trade publications. With use of PLC and other production and material efficiencies, CarbonKind eliminates a large portion of CO2 that would be typical of OPC products and provides low-carbon CMU produced with proven, sustainable market methods. It does not rely on nascent technologies that are not quite ready for a real-world production environment.
CarbonKind by Angelus Block achieves the largest CO2 reductions for CMU in the Southern California region.
CLF Material Baselines and Angelus’ CarbonKind CMU
Our collection of EPDs demonstrates how this is translated into reduced global warming potential impacts (GWP). Current versions show further declines in GWP values. Emphasis is on Medium Weight CMU, as this density class is the most widely used. The average Angelus Medium Weight GWP is 160 kg CO2e per m3, and fares extremely well compared to the Climate Leadership Forum’s (CLF) Material Baselines, with GWP values 57% and 71% less than CLF Typical and Baseline values. CMU were included in the 2021 CLF Material Baselines v2, where Typical and Baseline values were generated based on review of available EPD and LCA data.
The 2023 CLF Material Baseline takes a different approach and relies on industry-wide EPDs. Whereas Canada had sufficient industry-wide EPDs for the 2023 version, the U.S. did not. Here, EPDs are company-specific, and some, like ours, are location and product specific. Based on lack of industry-wide EPDs at the time of publication, CLF chose to not include U.S. data. However, in 2023’s Appendices, CLF did note the EPDs it deemed acceptable. Sources for those EPDs were predominantly from California.
Again, average Angelus Medium Weight GWP compared quite well against these values.
CMHA Industry-Average EPD for CMU in the U.S.
Subsequent to the 2023 CLF baselines, the Concrete Masonry & Hardscapes Association (CMHA) released the first U.S. industry-average EPD. The EPD was created by collecting data from 35 concrete masonry producers across the U.S.
Once again, Angelus' CarbonKind CMU are significantly lower in GWP—by 34%—when compared with the U.S. industry average.
CarbonKind fully meets ASTM C90 and is available in all Angelus-produced CMU. Angelus Block is fully committed to advancing the sustainable contributions of concrete masonry and offers CarbonKind products without a cost premium.
LEED Benefits
With data now available from CLF, comparisons to baselines are possible. A new LEED v4 and v4.1 Pilot Credit, Procurement of Low Carbon Construction Materials (MRpc132), provides means to account for and define reductions in the embodied carbon of materials, and ultimately the building. Angelus CarbonKind CMU significantly contribute to the intent of this pilot credit.
There's More to Concrete Masonry
The tremendous improvements offered with CarbonKind CMU provide a potent element to an optimized concrete masonry wall utilizing high SCM masonry grout. They're a powerful carbon-cutting combo. See more:
Concrete Masonry: An Optimized Low Carbon Wall
Masonry Grout: Cement Replacement Studies
After manufacture, CMU have exceptional carbon uptake potential, absorbing atmospheric CO2 at notable rates. In 2022, ASTM international published Conceptual Test Protocols for Measuring Carbon Sequestration of Manufactured Dry-Cast Concrete Products4. This methodology for measuring carbon sequestration has since become a widely accepted standard and has had a significant impact in reducing GWP values for CMU. See Carbon Uptake of Concrete Masonry.
1 2021 Material Baselines - Carbon Leadership Forum
2 Waldman, B., Hyatt, A., Carlisle, S., Palmeri, J., and Simonen, K. (2023). 2023 Carbon Leadership Forum North American Material Baselines, Category Appendices. Carbon Leadership Forum, University of Washington. Seattle, WA. April 2023. http://hdl.handle.net/1773/47141. C1: Masonry - CMU
3Concrete Masonry & Hardscapes Association - Industry Average Environmental Product Declaration
4Walloch, Craig & Powers, Laura & Broton, Donald & Thompson, Jason. (2022). Conceptual Test Protocols for Measuring Carbon Sequestration of Manufactured Dry-Cast Concrete Products. 10.1520/STP164020210112.
