With more focus than ever on embodied carbon in construction, demand for low carbon building materials is increasing. But what is low carbon concrete and how can it be adopted on a broader scale to help the industry meet its carbon reduction goals without negatively affecting the concrete industry?
This blog post addresses all these questions and more:
- What is Low Carbon Concrete?
- Why Traditional Concrete Has a Large Carbon Footprint
- Increasing Demand for Low Carbon Concrete
- How to Produce Low Carbon Concrete
- Low Carbon Ready Mix Concrete
- Low Carbon Precast Concrete
- Low Carbon Concrete Projects
What is Low Carbon Concrete?
Low carbon concrete is concrete produced with a lower carbon footprint than traditional content. Other than a reduced carbon footprint, low carbon concrete should behave identically to its high carbon counterpart.
To create low carbon concrete, producers can implement a series of relatively low-impact changes to their production processes and mix designs. For example, switching fuel source, replacing some cement content with mineral compounds like calcined clays, fly ash, or blast-furnace slag, or using new technologies like CarbonCure’s suite of products.
In September 2020 the Global Cement and Concrete Association released a Climate Ambition pledge that aspires, not just to low carbon concrete but, to carbon neutrality across the industry by 2050. Many cement and concrete companies have already signed this commitment and have had their strategies third-party verified by the Science Based Targets initiative.
Concrete’s Path to Decarbonization
Why Traditional Concrete Has a Large Carbon Footprint
Concrete plays a vital role in our daily lives through many diverse applications and usages. It shapes the built environment around us, from schools, hospitals, and housing, to roads, bridges, tunnels, runways, dams and sewage systems. In fact, concrete is the most used man-made material in the world, with three tons used annually for each person on the planet.
Cement—the key ingredient that gives concrete its strength—is produced by burning limestone in kilns at 2,300° to 3,000° F (1,260° to 1,650° C). The process typically uses powdered coal or natural gas as fuel, consuming a large amount of energy and releasing carbon dioxide (CO2) from the combustion.
- One ton of Portland cement produces one ton of CO2 emissions
- Cement accounts for 7% of all global carbon emissions
- Concrete is responsible for 50-85% of the embodied carbon in any building project
If it was a country, the concrete industry would be the third-highest emitter of CO2 after China and the United States. Yet worldwide demand for concrete is second only to water. That’s because concrete is the most resilient material on the planet—we are challenged with reducing its carbon footprint so we can continue to take advantage of its strength, flexibility, and durability for generations to come.
Increasing Demand for Low Carbon Concrete
A search of construction project databases indicates that over 4,500 construction projects across the United States have asked for Environmental Product Declarations (EPDs) within the past year (Dodge database search in May 2022).
This demonstrates the increased market demand for more transparency into the carbon footprint of building products.
Architects, engineers, contractors, and project owners are under pressure to prove they are meeting sustainability commitments to end clients and to professional initiatives and organizations like Architecture 2030, Structural Engineers 2050 Challenge, the Carbon Leadership Forum, and the World Green Building Council.
This push will increase in the coming years, particularly in the United States where the federal Buy Clean requirements come into effect on January 1, 2023. From that date, the General Services Administration and other government purchasing agencies must obtain Type III EPDs for all building materials used on federal projects. Once EPDs become mandated by the federal government, pressure will increase at the state level and in the private sector, too. Learn more about EPDs.
How to Produce Low Carbon Concrete
There is no silver bullet for the production of low carbon concrete. Concrete is made up of so many ingredients, so there are lots of ways to reduce the carbon impact of the individual components and processes.
Most of the carbon reduction and carbon removal innovation effort is focused on three key areas: low-carbon fuels, low-carbon blended cement, and carbon capture, utilization, and storage technologies.
In a recent CarbonCure webinar, Adam Auer, Vice President of Environment and Sustainability at the Cement Association of Canada, and Matt Dalkie, Technical Services Engineer at Lafarge Canada Inc., discussed some of these new technologies:
1. Low-Carbon Fuels
The concrete industry has been focused on fuel efficiency for a number of years for both cost-reduction and carbon-reduction reasons. More recently, the industry began evaluating the move from traditional fuels (e.g. coal) to low-carbon fuels (e.g. renewable natural gas), waste fuels (e.g. non-recyclable plastics, non-recyclable tires, rail ties, etc.), and potentially even carbon-neutral fuels.
According to Matt Dalkie, Technical Services Engineer at Lafarge Canada, these alternative fuels can reduce the carbon emissions of cement manufacturing by up to 40%, depending on how you treat the specific materials from a carbon perspective within the carbon calculation. However, there are some limitations based on the type of technology used for clinker manufacturing and the local availability of such fuels.
2. Low-Carbon Blended Cements
Most producers are already using Portland Limestone Cements (PLCs) and supplementary cementitious materials (SCMs) in their cement or concrete mixes. Further optimizing the use of these materials could reduce cement and concrete emissions greatly.
For example, PLCs use uncalcified limestone in the cement grinding phase of the manufacturing process and can reduce the carbon footprint of concrete by 5-10%. SCMs—which include things like fly ash and slag—can reduce the amount of cement required in a concrete mix, thereby reducing the carbon emissions by up to 30%. Fly ash, for example, is a byproduct of the coal-fired power generation and can replace 30-50% of the cement in a concrete mix, reducing the carbon footprint by 10-20% depending on the replacement level specified.
However, with coal-fired power generation winding down globally, the availability of fly ash is becoming increasingly constrained. Slag is a byproduct of the iron manufacturing process and can replace 40-50% of the cement in a mix and up to 90% for some specialty applications. The carbon reduction from slag can be up to 30% depending on the replacement level specified.
It’s important to note that some of these solutions have durability and finishability implications in certain applications and, as a result, are not accepted in all specifications.
3. Carbon Capture, Utilization, and Storage Technologies
Innovation in carbon capture, utilization, and storage (CCUS) technologies is arguably the most exciting development in the concrete industry.
Carbon capture makes it possible to capture up to 100% of the carbon emissions from cement manufacturing. These captured emissions can be stored safely underground, injected back into concrete to strengthen it, or used to make other products like synthetic aggregates or fuels.
Some of the key players in the CCUS space include: CarbonCure, Blue Planet, Solidia, Svante, and Carbon Engineering. Read the full blog post for more details on each of these technologies.
Case Study: Low Carbon Ready Mix Concrete
Lauren Concrete has always been an early adopter of new technologies that can help the company on its mission to deliver world-class service to customers, employees, and its communities. With a growing emphasis on sustainable building in the markets it serves, Lauren Concrete saw an opportunity to gain first-mover advantage with low carbon concrete.
Following the successful implementation of new technologies like GPS tracking to enhance fleet optimization, software for real-time quality monitoring, and sensors for gathering strength and temperature data, Lauren Concrete was eager to explore technologies to deliver greener concrete to its customers. CarbonCure was the next logical step on Lauren’s innovation journey.
CarbonCure manufactures technology for the concrete industry that introduces recycled CO₂ into fresh concrete to reduce its carbon footprint without compromising performance. Once injected, the CO₂ undergoes a mineralization process and becomes permanently embedded. This results in economic and climate benefits for concrete producers—truly a win-win.
To date, Lauren Concrete has saved a total of 6,413 tonnes of CO2 emissions—that’s the equivalent of carbon dioxide 8,337 acres of trees absorbing concrete for one year.
Case Study: Low Carbon Precast Concrete
CarbonCure Precast works by injecting recycled carbon dioxide (CO2) into fresh concrete during mixing. Once injected, the CO2 undergoes a chemical reaction where it transforms into a mineral. This improves the compressive strength of the concrete, allowing for the reduction of cement content in mix designs. Cement production is a carbon-intensive process so reducing its use can significantly improve the carbon footprint of precast and prestressed concrete.
Coreslab Structures (TEXAS) Inc. was seeking ways to reduce its carbon footprint in an efficient and non-disruptive way. It began working with CarbonCure in 2020 when a client—Compass Datacenters—requested the use of low carbon concrete in a new data center in Texas. Compass prides itself on being a good steward of the environment and considers its impact in every area from construction through to operations.
“Our data centers use concrete in many areas, from foundations and sidewalks to precast walls and roofing. We estimate using CarbonCure will reduce our CO2 footprint by an average of 1,800 tonnes (1,984 US tons) per campus. That’s the equivalent CO2 sequestered by 2,100 acres (850 hectares) of forest or driving a car 6.4 million kilometers (4 million miles),” said Nancy Novak, Chief Innovation Officer at Compass Datacenters.
Coreslab (TEXAS) implemented CarbonCure to meet the needs of its client. The team was impressed with the ease of implementation and the volume of cement reduction. As a result, Coreslab added CarbonCure to almost all precast mix designs and is now experiencing cost savings of approximately $1,000 USD per day. Coreslab (MISSOURI) and Coreslab (ARIZONA) have followed suit and expect to see similar results. Read more about Coreslab Structures and CarbonCure Precast.
Low Carbon Concrete Projects
If you have any hesitation about the application of low carbon concrete in any type of construction project, visit CarbonCure’s reference library to read a variety of case studies featuring all types of construction from residential to commercial including projects like:
Amazon HQ2 is part of the Metropolitan Park site, an existing urban renewal and development project in National Landing.
The first phase of its “ground-up” construction will see the redevelopment of a block of vacant warehouses into two new LEED Platinum-certified buildings, new retail space for area businesses, and plenty of open space for the community to enjoy. These buildings are the first step to creating an urban campus where Amazon’s future 25,000 employees and the local community can live, work and play.
Miller & Long and Vulcan Materials delivered an estimated 106,555 cubic yards (81,467 cubic metres) of concrete made with CarbonCure, which will save approximately 2,522,000 pounds (1,144 tonnes) of CO2.
725 Ponce Street, Atlanta, Georgia
Thomas Concrete delivered 48,000 cubic yards (36,699 cubic meters) of concrete made with CarbonCure to 725 Ponce Street in Atlanta, Georgia—a USD $190 million mixed-use development clocking in at 360,000 square feet (33,445 square meters). The use of CarbonCure on the project diverted 680 metric tons CO2 from the atmosphere—equivalent to 888 acres of forest absorbing CO2 for a year. Rob Weilacher, Engineer of Record at Uzun+Case said, “We specified Thomas Concrete with the CarbonCure Technology to reduce the carbon footprint of 725 Ponce. We’re proud to have saved 1.5 million pounds [680 metric tons] of CO2 while maintaining our high-quality standards for concrete.”
Fox Hill Business Park, Greenville County, South Carolina
Fox Hill Business Park is a Class A business park covering 2.5 million square feet (232,258 square meters) in Greenville County, South Carolina. Sudler—the family-run commercial real estate company that manages it—recognized the strong long-term growth potential of Greenville County and wanted to find a way to make a splash with the new development. The company connected with Thomas Concrete to supply low carbon concrete to the project. Thomas Concrete addressed any technical questions about CarbonCure from project stakeholders. Ultimately the project stakeholders, including Buchanan Concrete and Pattillo Construction Corporation, came on board and the use of CarbonCure’s concrete solution saved more than 60 metric tons of CO2 on the project.
Infosys Technology and Innovation Hub
For Phase 1 of the Infosys project, Irving Materials Inc. (imi) used 8,000 cubic yards of 3,000, 4,000 and 6,000 psi mixes made with CO₂. The success of the phase was celebrated by imi and project developer Browning Construction.
“We pride ourselves at Browning for not only understanding how a building functions for a client, but how it fits into their corporate culture and core values. In addition to constructing a sustainable building, working towards pollution prevention is one of Infosys’ environmental protection initiatives. Utilizing CarbonCure's technology was a great fit,” said Scott Hirschman, AIA, NCARB, President of Construction, Browning Investments