Low-Carbon Concrete in the Northeastern United States
State Procurement Guide
Why Procurement Matters: Advancing Climate Leadership
Although concrete is one of the most carbon-intensive materials in our built environment, many opportunities exist to reduce its environmental impact. Through years of innovation, the concrete industry has generated solutions that can substantially reduce emissions while ensuring products meet the same performance standards of conventional concrete. These solutions, both mainstream and leading-edge, are available today to cement and concrete suppliers in the Northeastern United States (Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, New York, New Jersey, and Pennsylvania).
Because nearly one-third of all concrete used for construction in the United States is procured by state and local governments, public purchasing policies are seen as straightforward, preemptive solutions to reduce the carbon impact of buildings and construction. Purchasing low-carbon concrete for state projects will incentivize emissions reductions in the local concrete industry and help reduce economy-wide greenhouse gas emissions.
What Is Low-Carbon Concrete?
Concrete is made up of cement and other ingredients, and it can be cast on-site, precast (fabricated off-site), or purchased in the form of masonry units or blocks. Concrete suppliers tend to be highly localized to minimize transportation of wet (cast on-site) concrete to the construction site, whereas cement manufacturing is more centralized. Cement is created by heating limestone in a kiln to produce a substance called clinker, which is then ground down into a cement powder and mixed with water and aggregates (particles of sand and rock) to produce concrete.
While cement makes up only a small portion of the concrete mix by volume, it accounts for up to 90 percent of the total carbon embodied in the material due to the energy required to make clinker. As such, replacing a portion of the cement with alternate binding ingredients known as supplementary cementitious materials (SCMs) is one of the most effective ways to reduce the carbon content in concrete.
Concrete producers can reliably substitute approximately 40 percent of traditional cement with low-carbon alternatives. In the United States alone, increased deployment of SCMs could save 27 megatons of carbon dioxide equivalent (Mt CO2e) every year from current levels — roughly equal to taking 5.9 million cars off American roads.
Other solutions include using recycled concrete as aggregate, improving cement kiln efficiency, and employing innovative technologies that trap carbon in concrete during the mixing or curing process. The table below describes each strategy and their applicability in the Northeast:
Exhibit 1: Concrete Emissions Reduction Pathways
|Supplementary cementitious materials (SCMs)||Replacing portions of cement in concrete mixtures with SCMs reduces costs and emissions associated with cement usage.||Both well-established and emerging SCMs exist.||Fly ash, silica fume, and ground granulated blast furnace slag are the most widely used SCMs in the Northeast. Ground glass pozzolan is newly available to concrete suppliers but is not yet commonly used.|
|Portland limestone cement (PLC)/Type 1L||The production of clinker in cement manufacturing is a carbon-intensive process. Using limestone in blended cement can reduce the amount of clinker needed — and the associated carbon emissions.||Well-established||Type 1L cement is available in some areas but is not yet abundant throughout the Northeast.|
|Recycled concrete aggregate (RCA)||Concrete is crushed and recycled as aggregate for new concrete used for nonstructural applications, such as base layers for roads, parking lots, driveways, and backfill material.||Well-established||Concrete that is returned to ready-mix sites is commonly reused as aggregate.|
|Cement kiln efficiency and fuel switching||Emissions can be reduced through measures such as switching kilns to biomass or other alternative fuels and through simple efficiency upgrades on existing equipment.||Well-established||These approaches are applicable to cement kilns in the Northeast.|
|Carbon capture and storage technology||Innovative technology enables concrete to capture and store carbon dioxide through a mineralization process during mixing or curing.||Emerging||Use of this emerging technology is not widespread in the Northeast.|
What Is the Carbon Impact of Concrete?
Environmental Product Declarations (EPDs) are the standard method of reporting the carbon content of concrete and other construction materials. Concrete EPDs disclose a variety of environmental impacts associated with the manufacturing process, including global warming potential (GWP), which is a measurement of the total GHG emissions per unit of concrete. Information on how manufacturers produce EPDs is described in the next section.
The average GWP of ready-mix concrete products in the Northeast tends to be higher than the national average (as seen in Exhibit 2). Other concrete products such as precast concrete and concrete masonry units are omitted due to lack of available EPDs.
Exhibit 2: GWP of Ready-Mix Concrete Products in the Northeast Compared to National Average
|Product Type||EPDs Available in Northeast||Northeast Average GWP (kg CO2e)||National Average GWP (kg CO2e)|
|Ready-Mix Concrete (2,500 psi)||104||255||247|
|Ready-Mix Concrete (3,000 psi)||975||305||276|
|Ready-Mix Concrete (4,000 psi)||2,545||342||307|
|Ready-Mix Concrete (5,000 psi)||2,339||369||325|
|Ready-Mix Concrete (6,0000 psi)||673||386||346|
|Ready-Mix Concrete (8,0000 psi)||22||356||346|
Note: The Northeast includes Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, New York, New Jersey, and Pennsylvania.
As of the date of this publication, 8,421 ready-mix concrete EPDs across all compressive strengths are available from manufacturers located in the Northeast. The table below details which manufacturers created these EPDs.
Exhibit 3: Manufacturers with EPDs Available from Plants Located in the Northeast
|Manufacturer||EPDs Avialable in Northeast|
|Aggregate Industries USA||249|
|Gotham Ready Mix||96|
|O & G Industries||84|
|Brewster Transit Mix||13|
Note: Aggregate Industries USA is a large subsidiary of the international corporation LafargeHolcim.
How Are EPDs Created? What Are the Costs?
Most procurement policies require disclosure of the embodied carbon impact of concrete through third party–verified, Type III Environmental Product Declarations (EPDs), which are provided by the concrete supplier. To create an EPD, a supplier must engage with a third-party service provider to conduct a life-cycle assessment for the product. A list of service providers in the United States can be found in the Appendix. The process typically includes:
- Data collection: The service provider collects data on the inputs to the product, energy consumption for production, and chemical process emissions. The data required for EPDs is routinely tracked by manufacturers for cost, quality control, and regulatory purposes, making it easily available for collection.
- Life-cycle assessment and EPD report generation: The service provider must follow designated ISO standards as well as product category rules, which spell out a predetermined set of requirements and guidelines for conducting a life-cycle assessment.
- Verification and publication: Once generated, the EPD is verified by a third party and made available to the public.
- Expiration: EPDs expire after five years, after which the process can be restarted.
EPD providers structure pricing per concrete plant, rather than per EPD. Based on a survey of three popular EPD providers in the United States, access to unlimited EPDs for a single concrete plant includes an initial setup fee ranging from $3,000 to $5,200 for the first year, with subsequent annual subscription fees ranging from $1,500 to $2,990. Some providers offer cost tiers based on features and licensing types and/or pricing discounts for multiple plants. In one example from Climate Earth, a concrete company with five plants would pay an initial setup fee of $8,200 and subsequent annual fees of $4,750 — equating to $1,640 per plant for the first year and $950 per plant for subsequent years.
Third-party verification costs are separate fees that vary based on the complexity of the products and the number of EPDs submitted at once. For a single EPD, costs can be as high as $2,000, whereas a bundle of up to 14 EPDs submitted together can be verified for approximately $10,000.
As demand for low-carbon concrete products expands throughout the Eastern United States, local concrete and cement suppliers will respond by confidently investing in EPDs and carbon reduction solutions to differentiate themselves in an increasingly competitive marketplace. Providing initial financial support in the form of grants, tax breaks, or performance bonuses to aid small businesses with the production of EPDs can accelerate the market and may be a critical component to the success of procurement policies in areas where very few manufacturers currently offer EPDs.
What Are the Other Costs and Benefits to Manufacturers?
Each emissions reduction solution described in Exhibit 1 yields benefits to concrete suppliers or cement manufacturers, but all require varying degrees of up-front investment.
Introducing new SCMs to a concrete mix recipe requires approximately six months of research and testing to ensure the final product meets all performance requirements. Furthermore, SCMs and recycled concrete aggregates (RCAs) need to be stored in separate silos that can take up real estate on space-constrained ready-mix sites. However, once these initial investments have been made, SCMs can reduce the cost of the cement blend by up to $45/ton and even provide increased durability and other technical advances over traditional mixes. The use of RCA can reduce costs as well, particularly when the aggregate is processed on-site. For nonstructural applications, using RCA on the same site where it was sourced offers a direct cost savings of 60 to 80 percent as compared with natural aggregate.
For cement manufacturing, fuel switching from coal to sustainably produced biomass-based fuels would likely increase fuel costs. Kiln efficiency improvements could help limit this impact by reducing the amount of biomass fuel required. Fuel costs also vary significantly based on the proximity of the cement producer to a suitable biomass source.
What Are the Costs and Benefits to Buyers?
Some contractors may be unfamiliar or hesitant to work with low-carbon concrete due to the mixes needing slightly longer curing times than conventional products. However, once cured, low-carbon concrete performs the same as conventional products. Some low-carbon concrete products can even provide improved compression strength, which enhances performance.
The cost of concrete varies regionally. In a national marketplace survey conducted by the US General Services Administration, over 55 percent of the 130-plus businesses surveyed said that their low-embodied carbon products cost about the same as their conventional concrete products. In a recent interview with RMI, a Massachusetts supplier indicated a small cost premium for low-carbon concrete of $2–$20 per cubic yard (based on the strength of the mix) as compared to conventional products. These cost premiums are likely to decrease as more local suppliers offer low-carbon mixes. In regions where low-carbon concrete is the norm, such as in the Western United States, low-carbon mixes can be purchased with a cost premium of less than 1 percent. In the Puget Sound area, the overall carbon impact of concrete mixes dropped by 18 percent in 2021, without an increase in cost to the consumer.
What Are the Environmental and Human Health Benefits and Impacts?
The high carbon content of concrete is primarily driven by the manufacture of one key ingredient: ordinary Portland cement. The cement manufacturing sector is the third largest industrial source of pollution in the United States, with annual emissions of over 500,000 tons of sulfur dioxide, nitrogen oxide, and carbon monoxide. These emissions are associated with environmental impacts such as ground-level ozone (smog), acid rain, global warming, and water quality deterioration. Reducing emissions in the cement industry will help abate health issues associated with these emissions including visual impairment, adverse effects on the cardiovascular and central nervous systems, and respiratory problems.
Many low-carbon concrete producers reduce emissions by replacing a portion of the cement in each mix with SCMs such as fly ash, silica fume, and ground granulated blast furnace slag. The SCMs commonly used in the Northeast have some associated health risks as raw materials, but using them in concrete mitigates the hazard they may pose to human health and the environment.
Significant exposure to raw fly ash, for instance, is a human health hazard due to the presence of acidic, toxic, and radioactive elements including lead, arsenic, mercury, cadmium, and uranium. Fly ash is a by-product of coal-fired power generation and is typically stored on-site or disposed of in open landfills or wet ponds. The disposal of fly ash in landfills and ponds can damage human health and the environment through groundwater contamination. Its use in concrete, however, diverts millions of tons of fly ash from these storage sites each year. When mixed with cement, the heavy metals contained in fly ash are entrapped in the cured concrete via a chemical immobilization process. An analysis by the US Environmental Protection Agency found that the environmental releases from concrete containing fly ash were comparable to or lower than those from ordinary concrete.
Ground granulated blast furnace slag (GGBFS) is a by-product of steel manufacturing composed of calcium, silicon, and iron, with trace amounts of chromium, which is known to be hazardous to environmental and human health. Scientific investigations into chromium and other trace amounts of elements found in GGBFS have shown that the stabilization process that occurs when these elements are mixed with cement immobilizes the contaminants. No chromium or other trace elements were detected in various recent leaching tests from cured concrete made with a mixture of GGBFS and cement.
Ground glass pozzolans, which are readily available in the Northeast, are an emerging alternative to fly ash and GGBFS. This material uses postconsumer and postindustrial waste glass that cannot be used in other recycling streams, has approximately half the global warming potential impact of cement, and is free of heavy metals in its raw format.
Although concrete is frequently described as a “hard-to-abate” sector of the economy, opportunities abound for carbon reductions using proven and scalable technologies. By signaling demand for low-carbon products, government entities can help accelerate the transition to a net-zero future while significantly reducing the climate and negative health impacts of their construction activities.
|Climate Earth||EPD operator, third-party verifier, sustainability consulting|
|ASTM International||EPD operator, third-party verifier, performance standards issuer|
|NRMCA||EPD operator, industry association|
|Athena Sustainable Materials Institute||Third-party verifier, sustainability consulting|
|PRé Sustainability||Third-party verifier, sustainability consulting|
|NSF International||EPD operator, third-party verifier|
|CSA Group||EPD operator, performance standards issuer|
|IBU||EPD operator, third-party verifier|
|One Click LCA||Large-scale EPD generation software, verification and publishing services|
|EPD Hub||Verification, publishing|
- Allister Melvin, Technical Services Manager, Aggregate Industries Northeast Region, personal communication, March 23, 2022.
- Michał Łach et al., “Geopolymers as a Material Suitable for Immobilization of Fly Ash from Municipal Waste Incineration Plants,” Journal of the Air & Waste Management Association 68, no. 11 (2018): 1190–1197.
- Representatives from One Click LCA, Athena Sustainable Materials Institute, and Climate Earth, personal communication, April 2022.