Contractors are facing increasing pressure to deliver lower-carbon projects, and concrete plays a major role. While cement production has traditionally been emissions-intensive, new approaches are helping reduce carbon while maintaining strength, durability and cost performance.
“There’s going to be increased demand for concrete as the built environment expands,” says Brian Killingsworth, executive vice president, local paving at National Ready Mixed Concrete Association. “So we’re going to have to be innovative.”
In practice, this means that contractors now have more options than ever to reduce carbon without increasing cost or sacrificing performance.
“There’s going to be increased demand for concrete as the built environment expands, so we’re going to have to be innovative.”
Brian Killingsworth
National Ready Mixed Concrete Association
MORE EFFICIENT CONCRETE MIXTURES
Carbon can be significantly reduced by optimizing how much cement is used in each mix. Concrete structures should not be overdesigned, which can result in unnecessarily higher cement content.
Another good practice is carbon budgeting. Set a project-level goal of how much carbon will be reduced in the concrete used and then determine which concrete mixtures within the project can withstand carbon reduction.
Projects should use performance-based specifications, which allow contractors to develop innovative, lower-carbon mixtures—unlike prescriptive specs that limit materials or require minimum cement content.
ADMIXTURES
One of the most immediate ways to reduce carbon in cement is through admixtures that limit the amount of cement needed.
“With admixtures, now you get to be even more efficient with cement,” explains Lionel Lemay, founder and CEO at ConcreteNexus LLC.
Different types of admixtures serve different purposes.
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Water reducers. The most impactful are water-reducing admixtures. “The less water you use, the less cement you need in concrete to get the same kind of performance out of it,” Lionel notes.
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Strength enhancers. Other admixtures increase strength with same amount of cement. Conversely, if more strength is not needed, then contractors could use less cement and still meet the target strength.
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Modifiers. Viscosity admixtures make concrete more workable without adding water. There are also admixtures that accelerate the concrete set time in instances where the use of supplementary cementitious materials retard early age strength.
BLENDED CEMENTS
Beyond mix optimization, material innovation is also reshaping concrete’s footprint.
New types of blended cement products hold great promise for reducing carbon footprint in concrete. Already in use is Type 1L Portland cement with limestone that replaces some of the higher-carbon clinker in cement. Cement has also been blended with limestone, gypsum and calcinated clay.
Manufacturers are now developing blended cement with limestone in combination with fly ash, slag and other pozzolans. Industry standards will then likely be amended to allow concrete producers to include additional amounts of these materials in blended cement to get an even lower carbon footprint.
SUPPLEMENTARY CEMENTITIOUS MATERIALS
Another major opportunity lies in replacing cement altogether.
Slag, fly ash and other pozzolans can also be combined with calcium hydroxide, a byproduct of the cement hydration process, to create more calcium silicate hydrate that holds concrete together. That way, less cement needs to be used.
“You’re lowering carbon footprint, oftentimes also lowering cost and getting a better performing concrete with higher strength and lower permeability,” Lionel explains.
Ground recycled glass could also be a seemingly unlimited source of low-carbon supplementary cementitious material. Other sources could include natural pozzolans like pumice and diatomaceous earth created by the fossils of small shell creatures.
CARBONATION AND SEQUESTRATION
Other approaches focus on capturing and storing carbon directly within the concrete itself.
Concrete naturally absorbs carbon dioxide from the air over time, locking it in as a solid mineral similar to limestone. This process can be accelerated by crushing recycled concrete, increasing the surface area exposed to air and speeding up carbon absorption.
Producers are also injecting captured carbon dioxide from industrial operations directly into concrete during mixing. This not only stores carbon within the material but can also improve strength, which reduces the need for additional cement.
Emerging methods are expanding these possibilities even further. Biochar, created from wood chips and agricultural waste, can be added to concrete to store carbon, while new technologies combine carbon dioxide with metal oxides to create carbon-mineralized aggregates.
The future of concrete won’t be defined by using less of it, but by using it better—mix by mix, project by project.
Lionel and Brian shared these insights in the CONEXPO-CON/AGG 2026 session. Concrete Innovations: Pathways to Reducing Carbon Footprint. Watch the full session by purchasing On Demand Education Access from the CONEXPO-CON/AGG 2026 show.
PHOTO CREDIT: SHUTTERSTOCK/IRENE MILLER
