Concrete is the world’s most widely used building material. Composed of water, aggregates (sand and/or gravel) and a cement binder, it can produce as much as 50% of the greenhouse gases (GHGs) related to the manufacturing, transportation, installation, maintenance and disposal of building materials. 

A significant culprit lies within Portland cement. Despite representing only 10-15% of the concrete mix, Portland cement contributes 80-85% of the total carbon footprint. It not only takes a lot of energy to heat limestone to 1,400⁰C, it also involves a chemical conversion of that limestone (which is responsible for about two-thirds of the CO2 output from the process) to turn it into clinker, which is then cooled, ground with gypsum and refined into cement. In fact, experts estimate that cement production is responsible for 7-8% of total global CO2 emissions.  

In 2025, PCL Construction field-tested three new types of low-carbon concrete. PCL collaborated with Heidelberg Materials (one of the world's largest suppliers of aggregates and concrete), engineering firms and a major e-commerce client with ambitious sustainability goals.

The field tests took place at PCL Seattle’s yard in Maple Valley, Washington. “Recreating real-world job-site conditions, we poured 25-by-25-foot slabs, 25-by-42-foot concrete tilt walls and a strip foundation,” says PCL’s construction manager on the project, Patrick McQueen. “We had our finishers, carpenters and laborers on site giving real-time feedback on the technologies, what they’re like to pour, what they’re like to finish and how they perform in a lift operation. It was really satisfying for the whole crew to be a part of this effort.”

Many owners and clients have their own commitments to sustainability, and PCL's experienced team of professionals can help realize those goals. There is also a growing policy emphasis on the reduction of the GHGs generated to produce, transport, install, maintain and dispose of building materials throughout their life cycle — known as “embodied carbon.” 

“Cities and towns around the world are developing procurement guidelines that drive towards lower and lower embodied carbon levels,” says Shane Mulligan, sustainability market manager with Heidelberg Materials. “Certifications like the LEED green building standard are also awarding more credits for reducing embodied carbon.”

But decarbonizing the life-cycle emissions of concrete can be a heavy lift. It requires a multi-pronged approach, one that includes:

Innovative Products and Technologies: Concrete blends like those in the Seattle field tests use new and different binding agents to reduce the amount of cement required to make concrete. “One of the new products contains no Portland cement,” says McQueen. “I’m not sure it’s even fair to call it concrete.”

Recycling and Reuse: End-of-life concrete can be crushed and reused as aggregate for such applications as a road base or even incorporated back into new concrete. Many cities are developing “urban quarries” where construction demolition debris is gathered for reuse. All concrete for the Seattle testing was either reused for ongoing yard operations or removed and recycled locally.

Alternative Low-carbon Fuels: Products destined for landfill, such as construction and demolition waste, non-recyclable plastics, non-recyclable textiles and fabrics, can be diverted to provide fuel for cement production.

Natural Carbonation: Remarkably, concrete “takes up” some CO2 from the air over time in a process known as carbonation. This process is maximized when concrete surfaces are exposed to air, which can be further amplified when the concrete is crushed at end of life and before reuse.

Carbon Capture and Storage (CCS): Last year, Heidelberg Materials began operation at the world’s first industrial-scale CCS facility at its cement plant in Brevik, Norway. The facility will capture about half the plant’s emissions, or 400,000 tons of CO₂ per year. Others are in the planning or execution stage, including one in Edmonton, Alberta that has completed extensive engineering and planning.

Collaboration: “It will take everyone — owners, design engineers, general contractors and suppliers — working together to meet objectives,” says Mulligan. “Early discussions are paramount if goals are to be met.”

Based in Germany, Heidelberg Materials is a regular PCL partner on projects across North America. Like PCL, the company has committed to being net-zero carbon by 2050. Driven by public policy and their own commitments, both companies were excited to be part of the Seattle tests.

A third-party testing agency provided extensive testing of the concrete throughout the entire operation. “We lifted the wall panels, set them on the footing and then set the walls back down as the final test,” says McQueen. “One of the technologies struggled during the finishing phase, but all three mixes showed real promise for use on job-sites in the near future.” 

PCL and Heidelberg Materials are scheduled to perform more tests for the same client again in 2026. “It was really satisfying to be part of this project,” says McQueen. “It’s an exciting development for our industry and the future.”