With more focus than ever on embodied carbon in construction, demand for lower 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 Lower Carbon Concrete
- How to Produce Lower Carbon Concrete
- Lower Carbon Ready Mix Concrete
- Lower Carbon Concrete Projects
What is Low Carbon Concrete?
Low carbon concrete is concrete produced with a lower carbon footprint than traditional concrete. Other than a reduced carbon footprint, lower carbon concrete should behave identically to its standard concrete counterpart.
To create lower carbon concrete, producers can implement a series of relatively low-impact changes to their production processes and mix designs. For example, switching their fuel source, replacing some cement content with mineral compounds like calcined clays, fly ash or blast-furnace slag, or using proven technologies like CarbonCure.
In September 2020, the Global Cement and Concrete Association (GCCA) released a Climate Ambition pledge that aspires, not just to reduce the carbon footprint of concrete but, to achieve 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.
Learn more: CarbonCure Webinar
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. Worldwide demand for concrete is second only to water.
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 roughly one ton of CO2 emissions
- Cement manufacturing accounts for an estimated 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.
As factors like population growth and urbanization drive increased demand for concrete, there will be increased pressure to reduce the carbon footprint of the industry.
Increasing Demand for Lower Carbon Concrete
The drive to lower emissions from concrete production begins with increased transparency. To understand the carbon footprint of their construction projects, buyers can request that suppliers provide Environmental Product Declarations (EPDs) showing standardized environmental information about the lifecycle impact of their products. Concrete EPDs provide the Global Warming Potential (GWP) for the concrete mix being poured for a particular job. For example, the U.S. General Services Administration (GSA), other federal government purchasing agencies and several state and local governments now mandate Type III EPDs for all building materials used on government projects. Learn more about EPDs.
Using EPDs, architects, engineers, contractors and project owners are under pressure to prove they are meeting sustainability and climate 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 months and years, particularly in the United States where the federal government and several states have launched Buy Clean initiatives which either limit the GWP of concrete supplied to certain projects or provide incentives like tax credits for achieving GWP goals.
How to Produce Lower Carbon Concrete
Production of lower carbon concrete requires a portfolio of solutions. Concrete is made up of many ingredients, so there are lots of ways to reduce the carbon impact of the individual components and processes.
Most of the carbon reduction 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
For a number of years, the concrete industry has been focused on fuel efficiency to reduce both costs and emissions. 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. waste biomass), and potentially even carbon-neutral fuels.
According to Dalkie, 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, both of which reduce cement content in concrete and the emissions required to produce the cement. Further optimizing the use of these materials could further 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 an additional 5-10%.
SCMs—which include 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.
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 and Svante. Read the full blog post for more details on each of these technologies.
Case Study: Lower 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 lower 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 licenses technologies across the concrete industry that introduce captured CO₂ into fresh concrete to reduce its carbon footprint without compromising performance. Immediately upon injection, the CO₂ mineralizes and becomes permanently embedded within the concrete material. This results in economic and climate benefits for concrete producers—truly a win-win.
To date, Lauren Concrete has produced more than 182,000 truckloads of concrete with CarbonCure's technologies and saved a total of more than 17,000 metric tons of CO2 emissions —that’s equivalent to the annual carbon sequestration capacity of more than 20,000 acres of trees.
Lower Carbon Concrete Projects
If you have any hesitation about the application of lower 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. This includes projects like:
Amazon HQ2 is part of the Metropolitan Park site, an urban renewal and development project in National Landing.
The “ground-up” construction features 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.
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 hundreds of metric tons of 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... while maintaining our high-quality standards for concrete.”
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
Footage of the project also caught the eye of Bill Gates, and was featured in a video on his blog Gates Notes.