Reinventing Concrete

By Alastair MacGregor, Contributing Author

Global population grown is an urgent issue. It means the world will need to build the equivalent of a New York City every month, for the next 40 years, according to Architecture 2030, a non-profit research organization that provides a roadmap for the building sector to achieve carbon neutrality. 

With new approaches, concrete has the potential to become a building block of a more sustainable future.

Earlier this year, the U.S. House of Representatives passed a bill on this matter with near-total support, and it was poised to pass in the Senate, too. Even more surprising than bipartisan agreement on any issue is the fact that concrete could be the topic that brings lawmakers together from across the aisle. 

The Innovative Mitigation Partnerships for Asphalt and Concrete Technologies Act provides $15 billion for low-emission cement, asphalt and concrete research and development. 

Why is this needed?

According to Engineering Failure Analysis, growing investments in infrastructure boom are making concrete the second most-used substance in the world after water – and that’s a sustainability problem. 

Concrete accounts for roughly 8% of total carbon dioxide (CO2) emissions. With more than 50 billion tons of aggregate (sand and gravel) used for concrete each year, the world risks running out of sand and is going to increasingly dangerous lengths to get it, according to the United Nations Environment Programme. 

Sustainable concrete is one key to achieving UN environmental goals, but its production hasn’t changed all that much, relatively speaking, since it was perfected in ancient Rome.

Now, innovators are giving this ancient material a sustainability glow-up, experimenting with everything from living concrete that repairs itself to concrete that stores energy as a battery substitute. These innovations are addressing much (but not all) of the concrete lifecycle, from what concrete is made of, to how it is produced, to how it performs.

Reducing Concrete’s Impact

Cement production accounts for the vast majority of concrete-related emissions, according to a study published in Nature. Some engineers are working to replace limestone, cement’s most polluting ingredient, by doubling the amount of coal ash used in cement mix, turning waste from coal-fired power plants into a useful resource that lasts longer and goes twice as far as today’s standard mix. 

This is significant for countries like Australia, where coal ash accounts for a whopping 20% of all waste. Yet, as the green energy transition accelerates, we could run out of coal ash over the long-term. Thus, other engineers have pursued a newer process: recycling old concrete from demolished buildings, providing a replacement for limestone.

Decarbonizing Production

What if we could link cement production to carbon capture, utilization and storage? Heidelberg Materials aims to do just that. The first project of this scale for the cement industry worldwide, when fully operational it will capture, use and or store an estimated 1 million tons of CO2 annually from its cement facility and the associated combined heat and power plant in Alberta, Canada.

This is just one solution. Some projects aim to use renewable energy in the cement production process, which could produce extremely low or even zero-carbon cement. Others are using electrochemistry to develop cement in place of the high temperatures typically used, offering a low-carbon alternative that has already been applied, with three tons used in Boston’s largest net-zero commercial building in the Seaport district. 

Improving Concrete Performance

While lowering production emissions can deliver significant benefits, innovations in concrete performance can also reduce the frequency with which it needs to be repaired and replaced, particularly in the face of increasingly extreme weather. Concrete needs to hold up to demanding environments.

Research has found that ultra-high performance concrete (UHPC) is five times stronger than conventional bridge deck concrete, 10 times more resistant to wear and 100 times more resistant to deterioration. And it’s already in use.

The Delaware Memorial Bridge pioneered North America’s first application of UHPC over the entire deck of a suspension bridge after a study in 2018 showed that an overlay of UHPC could extend the life of the existing bridge deck with far less cost and traffic disruption. 

Once applied, UHPC extended the service life of the bridge deck by at least 40 years with no maintenance needed, compared to a 10-year extension with traditional concrete.

In 2018, a study of the four lane, two-mile long Delaware Memorial Bridge showed that an overlay of UHPC could extend the life of the existing bridge deck with far less cost and traffic disruption than new construction. 

Over 70% of U.S. roads are located in snowy regions, where the use of snowplows and salt for deicing eventually takes a toll on the durability of the concrete. To address this, researchers are developing self-heating concrete, embedding concrete with paraffin to melt a couple of inches of snow without salt, sand or shovels. 

Latex modified concrete can also make it less vulnerable to cracks, an overlay material that forms a waterproof layer to protect infrastructure from damage over time.

But, what if we could engineer concrete that actually heals itself? Some researchers are experimenting with bacteria to create “living concrete” and enable cracks to repair themselves. But that’s not all that new concrete can do.

Carbon Consumer

It’s one thing to mitigate impact by reducing emissions from production and recycling materials and even reducing the need for maintenance. Now, researchers aim to transform concrete into a climate solution superstar.

One approach is to use new forms of concrete to spur adaptation to climate change. For example, the Defense Advanced Research Project Agency (DARPA) funded “Reefense,” a project that is using nature-based, biodegradable concrete to foster an oyster reef that cleans the water, provides habitat for the local marine ecosystem and can serve as a living breakwater that protects coastlines from storm waves and erosion. Other innovations are going beyond adaptation to mitigate emissions.

Interestingly, traditional concrete naturally absorbs CO2 over its lifetime, but not enough to outweigh the emissions from production. Recently, researchers developed concrete that can absorb CO2 at twice the typical rate without reducing its structural integrity. 

Building climate-adaptive cities is the goal for many urban developers, and this bio-receptive concrete with moss coating makes a standout appearance. By turning CO₂ and nitric oxide (NOx) into oxygen and removing particulate matter, the moss produces clean and healthy air throughout our cities.

Also on the horizon is a carbon-cement supercapacitor that can store energy. 

Compared to today’s batteries, these cement supercapacitors store energy much more efficiently, can charge more rapidly and sustain better performance over time. Since they release power quickly, the vision is to use this new material for power storage in roads or houses, helping to overcome challenges to the renewable energy transition.

Looking Ahead

Innovations in concrete may be faster to deploy thanks to progress in 3D printing, which reduces planning time, labor cost and waste. Comparatively affordable 3D-printed concrete buildings are already popping up around the globe.

Artificial intelligence (AI) promises to further accelerate progress in several ways. It can help validate the climate claims of the innovations outlined above and test critical factors like strength, quality and cure time. 

Companies like AIcrete are pioneering AI-optimized concrete mix designs, tailored to specific locations. This localized approach, informed by real-world data, offers a more effective solution to traditional, one-size-fits-all construction methods. 

Now, we need to move more quickly to commercialize proven, locally relevant innovations. The good news is that industry leaders are taking action through efforts like the Structural Engineering Institute’s 2050 Commitment to Net Zero, the Climate Group’s ConcreteZero, an initiative to create a global market for net zero concrete, and The Carbon Leadership Forum, which aims to eliminate embodied carbon in buildings, materials, and infrastructure.
Together, we are reimagining what concrete can do.

Alastair MacGregor is Property and Buildings Executive, at WSP in the U.S.