Carbon Cure CEU?

I recommend to talk with your local concrete contractors and / or concrete suppliers. Depending upon the project type, local climate conditions, location of the concrete in the project, and even project schedule, I have heard mixed results for Carbon Cure. Sometimes it is good. Other times not as much. Ask the experts in the field.

We recently had a conversation with a local supplier about a project where we had put Carbon Cure into the specification. His team felt (after some research) that they could see a 5% reduction at most with Carbon Cure, and we were told they would rather have the option to use "other" methods to reduce the GWP of the mix. We couldn't really pin them down on what they wanted to do as "other" (this is somewhat new around here), but Type 1L cement, fly ash, polycarboxylates, and several other ideas were thrown out as being better than Carbon Cure in their opinion. We're continuing conversations to try to pin down what might be reasonable in our region.

Allison, following up on Jon's comment, in the Seattle area, we are pretty easily getting 25% or better GWP reductions from NRMCA benchmarks without cost or schedule impacts by making 3 spec changes:  1. Type IL cement instead of I/II 2. Substitute 15-20% of your cement with slag 3. Switch cure times on non-time sensitive structural components from 28 days to 56 days.  Slag replacement requires longer cure times to reach design strength, but only a few structural components need early design strength such as PT slabs, crane foundations and temporary retaining walls.  These 3 spec changes are much more effective than the 5% savings we have heard CarbonCure can deliver.   Below is a summary of estimated GWP savings we recently got from a local concrete supplier after we extended the cure times to 56 days on non-time sensitive components.  They informed us that their savings estimates are better than 25% because they barge rather than truck their raw materials to their batch plants.  Obviously barging is not feasible for all suppliers across the country, but those that use barges have a unique advantage from a GWP reduction standpoint.  To ensure multiple bidders can compete, we plan to spec a minimum 25% reduction to the NRMCA benchmarks and let them identify how much GWP savings they can provide.  We are going to require bidders submit their mix design GWP savings estimates with their bid as part of the bid evaluation process.  You really don't even have to mandate Type IL cement or a min slag replacement %, just set a reduction goal after confirming feasibility with a local supplier and have them provide you with the benchmarks for your spec.   

1. Concrete Exposed to Weather mix - GWP=178.37 kg/CY vs. benchmark=299.10 kg/CY  (40.36% reduction w/15% slag)
2. Concrete Exposed to Earth mix - GWP=127.61 kg/CY vs. benchmark=269.49 kg/CY (52% reduction w/50% slag)
3. All Other Concrete mix - GWP=162.60 kg/CY vs. benchmark=269.49 kg/CY (40% reduction w/17% slag)
4. Concrete Shear Walls mix - GWP=246.07 kg/CY vs. benchmark=415.86 kg/CY (40% reduction w/17% slag)
5. Columns mix - GWP=184.59 kg/CY vs. benchmark=347.85 kg/CY (46% reduction w/ 20% slag)
6. Post Tension Slab mix - GWP=221.13 kg/CY vs. benchmark=347.85 kg/CY (36.4% reduction w/ 0% slag)