CarbonCure was recently named one of two winners of the $20 million NRG COSIA Carbon XPRIZE. And for good reason! It’s a cost-effective way to reduce the global warming potential (GWP) of any concrete mix by about 5%. But if you’re starting with a mix with above average GWP, then it’s a stretch to call the new mix “low-carbon,” even if it has CarbonCure.
This is why we need more mix-specific EPDs so designers can use actual GWP values as a design metric. CarbonCure is not a stamp declaring any mix that uses it “low-carbon,” but it’s often used as such in lieu of actual GWP data. There are CarbonCure mixes with GWP far below and far above that of NRMCA regional average concrete mixes. Only readily available mix-specific EPDs in a database like EC3 that can solve this problem. Other effective GWP reduction strategies for concrete include
- Build less
- Use Portland limestone cement (also known as GUL, or general use limestone) over regular Portland cement
- Be mindful of cure times rather than arbitrarily specifying strength at 28 days
- Move toward performance based requirements rather than specifying water/cement ratios or minimum cement content (perhaps even specify maximum cement content in lieu of EPDs)
- Supplementary cementitious material (SCM) replacement, though keep in mind that it’s cement content that matters. % replacement is just one way to achieve cement reduction.
- CarbonCure. A great next step would be for CarbonCure to encourage concrete suppliers using their product to produce mix-specific EPDs to show off their impact reductions and avoid greenwashing
- Use carbon sequestering products like Blue Planet aggregate
- Utilize precast for higher quality concrete (balanced against productivity pressures)
- Geopolymer / alkali activated materials
- Material substitution
(I’ll add to the list if anyone has other ideas in the comments!)
Buy Clean policies on local, state, and federal levels will help eliminate a frustrating catch-22 where concrete suppliers don’t want to spend money to produce EPDs because designers aren’t asking for them, but designers aren’t asking for them because concrete producers aren’t producing them. So take the first step and include EPDs in your specifications! Start the conversation. Bring up embodied carbon early and often, and make EPDs a part of that conversation.