In November, California’s Marin County adopted the world’s first building code that limits carbon emissions from concrete. (Concrete’s Portland cement content accounts for more than 6% of anthropogenic carbon emissions.) The code focuses on concrete performance, creating standards for composition that “maintains adequate strength and durability for the intended application” while reducing embodied carbon, according to the county website.
The code covers both residential and commercial construction and includes standards for a number of industry practices, including:
- replacing Portland cement with supplementary cementitious materials (such as fly ash, slag, and ground glass)
- minimizing the amount of cement in mixes
- selecting aggregate
- changing the requirements for how quickly concrete has to cure (which impacts the amount of cement used)
The code still allows the use of higher amounts of cement where that performance is needed.
The County of Marin Low Carbon Concrete Code only covers concrete placed in the local jurisdiction. It does not cover precast or concrete masonry units, nor other high-carbon materials such as steel, glass, or insulation. But the code lays the groundwork for research into other avenues for developing low-carbon concrete and has the potential to be adopted by other regional, state, or national code bodies and standard developers.
Development of County of Marin Low Carbon Concrete Code was funded in part by the Bay Area Air Quality Management District Climate Protection Grant Program and developed through a partnership that includes government, engineers and architects, academia, and the Carbon Leadership Forum, along with support from the U.S. Green Building Council (USGBC), the concrete industry, and other regional stakeholders.
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