ConcreteZero: providing a solid foundation for low carbon construction

After water, concrete is the most consumed material on Earth, and around 8% of global human-produced carbon emissions are a result of the production of cement, a key component of concrete.

With areas the size of Paris being built globally every single week for the next 40 years, the demand for concrete is significant, and highlights the need to drastically reduce the carbon emissions of this material if we are to achieve our net zero carbon goals of a 45% reduction on carbon emissions. 

ConcreteZero is a global initiative that brings together pioneering organisations to create a global market for net zero concrete. The initiative is led by Climate Group in partnership with World Green Building Council and World Business Council for Sustainable Development. Buro Happold was one of the founder signatories when ConcreteZero launched in July 2022.

The aim of ConcreteZero is to transition to 30% low emission concrete by 2025 and 50% by 2030, setting a clear pathway to using 100% net zero concrete by 2050. Our ConcreteZero commitments support Buro Happold’s wider sustainability goals of reducing the embodied carbon intensity of all of our new buildings, major retrofits and infrastructure projects by 50% by 2030. 

It is a well-known fact that the infrastructure sector will be heavily impacted by the consequences of climate change, so it is essential for the infrastructure team to take a proactive role in the reduction of concrete-related carbon emissions in our designs

Priscila Barban, Infrastructure engineer, Buro Happold

The Concrete Society’s Awards for Excellence in Concrete, held in London in November 2022, saw Buro Happold’s London College of Fashion project for UAL at Stratford Waterfront highly commended. 

The team looked to prefabrication wherever possible to ensure the quality of the exposed concrete finish while minimising risk on site. This resulted in two thirds of the vast concrete structural frame being created off site. The judges commented on the “exemplary” detailing achieved for the project. Having demonstrated our commitment to quality, we have now committed to improving the sustainability of our concrete designs through becoming a founding member of ConcreteZero.

But what exactly is low emission concrete? 

Low emission concrete has been defined as concrete with an embodied carbon intensity (kgCO2e/m3) of below a certain value depending on the strength of concrete used. The image below shows the threshold for embodied carbon intensity below which the concrete should fall. 

A graph displaying the threshold for embodied carbon intensity within concrete. Image: Climate Group

“Early client and contractor engagement is the step-change in behaviour required to maximise opportunities for low carbon concrete on projects” explains Ian Fiebelkorn, an associate in Buro Happold’s structural engineering team. “It is not sufficient for engineers to specify ultra-low carbon concrete without consultation, and expect this to be accepted in the current market.

“Bringing clients on board early, and working through the practical challenges of slower-curing sustainable mixes with contractors is an essential part of driving change in the industry, in the hope that one day these lower-carbon mixes will be the norm.” 

We are working collaboratively with other members of ConcreteZero across the supply chain to help define the future of specification. 

Ellie Moore, a senior structural engineer at Buro Happold says: “At the moment, the ConcreteZero threshold is achievable for concrete mixes with a high proportion of GGBS as a replacement for Ordinary Portland Cement, however GGBS is a material with a finite global supply so it cannot be relied upon as the solution.

“Instead, we must seek alternative and naturally abundant cement replacements such as limestone and pozzolana to use instead of, or alongside GGBS. Beyond this, we should look to more novel technologies to reduce the cement content and therefore the embodied carbon of our concrete products, such as geopolymers, alkali-activators and CO2 curing within the manufacturing process.”

She adds: “As part of this change, we may need to be less prescriptive with our concrete specifications, focusing only on the key performance requirements and allowing the supply chain more freedom in selecting the most suitable concrete mix to meet the required technical properties whilst delivering on the low-carbon threshold.”

An aerial image of the Parisian skyline.
Every week enough concrete is used globally to build an area the size of Paris. Image: Adobe Stock

Building sustainable infrastructure

Our ConcreteZero commitments also apply to our infrastructure projects, which arguably, use a lot more concrete than the building projects we work on. 

“It is a well-known fact that the infrastructure sector will be heavily impacted by the consequences of climate change, so it is essential for the infrastructure team to take a proactive role in the reduction of concrete-related carbon emissions in our designs,” says Priscila Barban, an infrastructure engineer at Buro Happold.

“By joining the ConcreteZero initiative, we aim to understand the options currently available, which may range from liaising with clients and contractors to understanding the construction critical path and specifying concrete mixes with lower carbon but longer curing times to reducing the volume of concrete to be used in a project.”  

It is an exciting time for material innovation and collaboration in concrete design, and by working together we can achieve our goal of a decarbonised concrete industry.