The Blended Cement Boom

The demand for lower-carbon cements in the US has quickly grown from a trickle to a flood, as sustainability continues to emerge as a key metric for end users on par with resilience and reliability. In a short time, the market has shifted significantly, with more advanced cement blends being developed for the future.

In some areas of the US, 100% of the cement currently being produced is portland-limestone cement (PLC). The rest of the country is moving in a similar direction, making blended cement the new default for modern construction projects. This blended material carries substantial environmental benefits, with up to 10% less embodied carbon than traditional portland cement. PLC offers a way for concrete producers to achieve a lower-carbon footprint, much like fly ash and slag cement have done for decades.

The transition to using greener cements has been underway for many years, but the pace has dramatically picked up recently as more producers, contractors, engineers, and architects have gained experience and confidence working with PLC. In 2020, blended cements like PLC represented about 3% of the 100 million metric t of cement consumed annually in the US. By 2024, blended cements grew to more than half of the total US cement consumption.

With this shift came significant climate benefits. In 2023, replacing traditional portland cement with PLC resulted in more than 3.9 million metric t of carbon avoided. That is roughly equivalent to a year’s worth of emissions from one coal-fired power plant, according to the US Environmental Protection Agency.

While traditional portland cement has long dominated the construction and infrastructure market in the US, blended cements offer an opportunity to maintain ambitious climate goals of net zero building without adding costs to projects. Traditional portland cement was patented almost 200 years ago, and challenges today call for new solutions.

In addition, those who have worked with PLC are realising benefits such as a lighter colour, which can be advantageous in certain architectural uses, and similar, or even improved, performance. A primary advantage is that PLC also offers carbon reduction with the ability to meet the same proven performance as traditional cement.

Contractors start with the same amount of PLC to replace portland cement, then test the mixture to confirm fresh and hardened properties. As the quantity of PLC produced in the US continues to grow, so does the number of projects it is being used in – and there are now numerous examples across the country that showcase the successes of blended cements.

Case studies

A prominent example of PLC being at the centre of a new project’s design is the new US$64 million training facility for the WNBA’s Seattle Storm. In construction, all the cement used was Type IL: the project used ASTM C595 Type IL PLC produced by Ash Grove Cement, a CRH company. As the team plays in Seattle’s Climate Pledge Arena, in a city that passed new building performance standards to reach net zero by 2050, sustainability was a critical key metric, leading the contractors to use PLC throughout the structure. The completed project not only exceeded LEED Gold standards but was also named a winner in the National Ready Mixed Concrete Association’s (NRMCA) 2024 Concrete Innovation Awards.

This same commitment to sustainability and responsible building was the driver behind the decision by the designers of Drexel University’s new Health Sciences Building in West Philadelphia to not only use PLC from Heidelberg Materials, but also source concrete materials locally. Some phases of the project used up to 25% Class F fly ash as a supplemental cementitious material to further reduce CO₂ emissions from concrete by up to 35%.

There has also been an increase in the number of roadway and other paving projects using PLC to reduce emissions without compromising performance. PLC was recently used in a project reconstructing a 4 mile stretch of California’s Highway 101, which Caltrans estimates will cut emissions by 28 000 tpy – the equivalent of taking more than 6000 cars off the road.

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