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.
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.
Angelus Block has taken a great system further with CarbonKind, a CMU with substantially lower CO2 impact. CarbonKind does not use higher-GHG ordinary Portland cement, 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 good 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.
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 203 kg CO2e per m3, and fares extremely well compared to the Climate Leadership Forum’s Material Baselines. 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 MB takes a different approach and relies on industry-wide EPDs. Whereas Canada had sufficient industry-wide EPDs, 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, CLF chose to not include U.S. data. However, in 2023’s Appendices, CLF did note the company and product specific EPDs it deemed acceptable. Sources for those EPDs were predominantly from California.
Again, average Angelus Medium Weight GWP compared quite well against these values.
|2021 CLF MB1
|Angelus MW Mean GWP
|2023 CLF MB Appendices2
|CLF MW Mean GWP
|Angelus MW Mean GWP
GWP values in kg CO2e per m3
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.
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. See Carbon Uptake of Concrete Masonry.