Now in its second year, the program recognizes outstanding achievement in concrete design and construction.
Early this month, the National Ready Mixed Concrete Association selected the winners of the 2024 NRMCA Concrete Innovations Awards. Ten projects demonstrate outstanding achievements in performance even as they lower environmental impacts, such as embodied and operational carbon footprints. To help you fully understand the great strides industry innovators are making to improve the resilience, performance and sustainability of concrete, I present these five examples of the top finishers in the Concrete Innovations Awards.
To set the tone, I implore you to remember the famous intro to The Twilight Zone. You are about to enter another dimension, a dimension not only of sight and sound but of mind. A journey into a wondrous land of imagination. Next stop, the Concrete Zone! Thanks to screenwriter, producer and narrator Rod Serling, and more importantly, all those in the concrete industry who are pushing the envelope to prove possible that which was unthinkable just a few years ago.
The Project Team of Prologis Nexus – Overall Winner
Wow factor: Reduced embodied emissions by 40 percent without relying on carbon credits.
Central Concrete Supply, a subsidiary of Vulcan Materials Co., partnered with Prologis, Whiting Turner, Bradley Concrete and HSA Structural Engineers with new technology to achieve huge reductions in embodied carbon emissions. The 260,000-sq.-ft., 40-ft.-tall, clear height industrial building in San Leandro, Calif., combines modern mix technology, structural design and common sense for carbon footprint reduction.
Project highlights:
- Reuse of ~65 percent of existing concrete walls and foundations.
- Optimization for slab-on-grade design using a high-performance concrete mix, reducing slab thickness from 9 to 6 inches.
- Low-carbon mix design to meet high-performance needs while being 12 percent below NRMCA’s 4,000-psi Pacific Southwest regional benchmark for global warming potential (GWP), expressed as kilograms of carbon dioxide equivalent (kg CO2e) per cubic yard.
Seattle Storm Center for Basketball Performance
Wow factor: Achieved 80 percent of 2030 targeted CO2 reductions for concrete set by the World Economic Forum’s First Movers Coalition.
Seattle’s Stoneway Concrete worked with contractor Sellen Construction to reduce embodied carbon and maximum cement limits in exterior tilt-up walls. An 80-percent slag cement mix was selected based on previous success with the Amazon Spheres project. Selected parameters for concrete were also specified with 56-day design rather than 28 days, further reducing the required amount of cementitious ingredients and GWP to achieve the required strength.
Stoneway used Lafarge slag cement, Ash Grove Type IL cement, plus Chryso and GCP admixture and fiber technologies to help meet the specified embodied carbon limits and exceed overall performance. The teams collaborated to identify the best low-carbon mixes for the intended application.
Gig Harbor Habitat for Humanity
Joe Sheehy, the Pacific Northwest area manager of Concrete at Heidelberg Materials, demonstrates the huge potential for carbon sequestration and ready mixed concrete. The project incorporates the BioLock admixture from Solid Carbon to sequester carbon (i.e., store carbon removed from the atmosphere in a carbon pool) in the 100-cubic-yard placement, setting a new standard for carbon reduction in concrete construction. Clark Construction was the general contractor.
Project highlights:
- Foundations: The industry average for 3,000-psi concrete with 0-19 percent fly ash is 345 kg CO2e per cubic yard. Sheehy’s team achieved a 68-percent reduction, 110 kg CO2e per cubic yard.
- Interior slab on grade: The industry average is 271 kg CO2e per cubic yard. Sheehy’s team achieved a 64-percent reduction, 97 kg CO2e per cubic yard.
- Insulating concrete form wall mixes: The industry average is 243 kg CO2e per cubic yard. Sheehy’s team achieved a 69-percent reduction, 76 kg CO2e per cubic yard.
Cement-Free Concrete in Hubbard’s Corner Project
Consider a world in which concrete can not only eliminate the carbon footprint of portland cement but also absorb even more carbon over time from the atmosphere. Too good to be true? Read on.
C-Crete has pioneered and deployed a breakthrough pourable cement-free concrete product that is essentially emissions-free and actually absorbs CO2 from the air over time. It also exceeds portland cement concrete in performance. The material was recently used in a commercial building in Seattle, called Hubbard’s Corner Project. Heidelberg Materials was the ready mixed company used for this pour. Key attributes of C-Crete:
- Cost parity with conventional cement/concrete (without any carbon tax/credit).
- Saves up to 1.1 tons of CO2 per ton of binder: ~800 kg CO2 by not using ordinary portland cement plus up to ~300 kg active CO2 sequestration in the binder.
- ASTM C1157, freeze-thaw, alkali-silica reaction, chloride/acid resistance.
- Compatibility with conventional admixtures.
681 Florida Street Affordable Family Housing
This pilot project for the Bay Area Low-Carbon Concrete Model Code is a first-of-its-kind effort to address embodied emissions in an area of local government control. Collaboration with concrete builders and suppliers achieved mixes with significantly lower carbon content. They attained a 36-percent reduction in embodied carbon of the concrete alone, which yielded a 23-percent reduction across the entire project. The result is a fossil fuel-free building with an energy use intensity that meets goals of the American Institute of Architects-aligned 2030 Challenge.
The embodied carbon reductions were entirely cost-neutral, allowing the ready mixed supplier greater flexibility in supplying supplementary cementitious materials. The methodology involves removing prescriptive requirements from the structural concrete specifications, such as water content and cement ratio, to instead focus on strength requirements and overall performance.
The process is meant to be minimally bureaucratic, involving a simple worksheet that gets added to the project plans upon permit submission and a verification worksheet submitted by the contractor. This and similar pilot projects have started appearing over the last few years and are being considered in other municipalities across California. While the model code is a technical step forward for more sustainable concrete, an even larger impact is the collaborative lessons that are spreading among designers, engineers, suppliers, builders and owners.
Equal to the Challenge
Let’s give Rod Serling the last word. “It is said that science fiction and fantasy are two different things. Science fiction is the improbable made possible, and fantasy is the impossible made probable.” Give a shout-out to all those citizens of the concrete industry pushing the impossible to the improbable and the improbable to the possible.
Craig Yeack has held leadership positions with both construction materials producers and software providers. He is co-founder of BCMI Corp. (the Bulk Construction Materials Initiative), which is dedicated to reinventing the construction materials business with modern mobile and cloud-based tools. His Tech Talk column—named best column by the Construction Media Alliance in 2018—focuses on concise, actionable ideas to improve financial performance for ready-mix producers. He can be reached at [email protected].