Geopolymer & High-Blend Cement – A pathway To A Lower Carbon Footprint

Environmental Leadership Is As Simple As Asking A Question

As I hold the small grey cube in my hand, it feels weighty – in more ways than one. There is a sense of expectation in the materials lab, as if this one little concrete sample will one day grow up to save the world. The cube’s creator looks on like a proud Dad.

“I can confirm this is concrete” I joke, trying to break a little tension before the technical onslaught to come.

A materials engineer at UQ, has kindly allowed me into his lab to see samples of concrete. The average person might roll their eyes with boredom at cement engineering, but people like this researcher are on the way to developing potentially game-changing technologies in the fight against climate change.

“That’s the point,” He says in reply to my feeble joke. “It’s almost mechanically identical but it produces 10% of the emissions compared to conventional cement. It’s the way all cement will be in 10 years’ time.”

Portland cement – or as you may know it, cement – is responsible for 8% of global CO2 emissions. The emissions from cement are greater than those from every car, truck, train and plane combined; yet cement is far down most people’s list of considerations when they think of fighting climate change.

“The thing is, cement production creates carbon dioxide in the same way wheat harvesting produces straw, it’s an unavoidable part of the process” – he emphasised.

He is referring to the chemical reaction used to produce lime, the active ingredient in cement. When cement is produced, limestone is heated to over 1,400°C, at which point it breaks down into lime and CO2.

The emissions from this chemical reaction make up around 55% of the total emissions from cement production. The other 45% is expended getting the kiln up to the scorching 1,400°C and grinding the tonnes of limestone into a fine powder.

These emissions are not insignificant and we’re going to need to address how we produce cement if we’re to have any chance of meeting Paris agreement goals.

“(The cement industry) in its current form, it will not be compatible with any nation’s commitment in the Paris agreement; and if radical changes do not occur the world will risk missing [its] climate goals.”

-Mike Disabato – The Outline.

There are two leading alternatives to Portland cement, geopolymer and high-blend cements.

Geopolymer cement

Geopolymer cement uses totally different chemistry to Portland. Instead of heating up limestone to 1,400°C and forcing it to spew carbon dioxide, geopolymer combines two chemicals to induce curing – much like 2-part epoxy glue. The production of these chemicals does have an impact on the environment, but this impact is far less than the impact of Portland cement.

Geopolymer cement is made from fly ash – currently an environmental problem, this waste product of coal fired power plants can supply our cement production needs for 20 years.

In Australia, the biggest project to use geopolymer cement is the Toowoomba Wellcamp airport. This airport used 51,000 cubic meters of concrete, avoiding 8,800 tonnes of CO2 emissions which would have occurred if conventional cement were used. This project was performed by Wagners, one of the nation’s leaders in low carbon cement. That amount of CO2 is comparable to 80,000 people switching from cars to commuting by bike for a year.

High-blend cement

High blend cement isn’t so much an alternative to Portland as an extension of it. High blend cement describes any cement in which a large portion (>30%) of the cement is replaced by other compounds. These compounds may perform one of three functions:

  1. React in a similar way to Portland cement
  2. Increase packing efficiency by filling gaps
  3. Increase reactivity of the reactive compounds

These replacement materials can be used in conjunction to replace 80% of the Portland cement in a mix which can lead to a 75% reduction in emissions. Add to this the fact that high-blend cement can be produced using existing equipment and we have a viable and competitive solution for the future of cement.

10-year roadmap

Beyond Zero Emissions, a leading Australian sustainability think-tank, propose Australia transition in the next 10 years to a system in which cement supply is 50% geopolymer and 50% high-blend. A leading factor in this transition is the fact that low carbon cement is cost competitive with conventional cement.

Low carbon cement is cost competitive with conventional cement.

At this early stage, supply is not universal but it is price competitive in many cases. For the forward thinking company looking to reduce the environmental impact of their construction project, it is as simple as knowing what’s possible and insisting on low carbon cement. Those who implement this material in its early stages will develop a reputation as thought leaders, and help accelerate the uptake of this critical technology.

Beyond 10 years

As we look beyond the next 10 years, the potential of today’s cutting-edge technology comes into play. Start-ups like Carbicrete and Solidia herald an age in which concrete is used as a weapon in the fight against climate change – a weapon we have sorely needed for some time.

“The plausibility of the Paris Climate Agreement’s goals rested on what was lurking in the UN report’s fine print: massive negative emissions … an unproven concept to put it mildly.” – Abby Rabinowitz & Amanda Simson – Wired.

Solidia and Carbicrete both produce cement which is not only carbon neutral but carbon negative. These products are in the early stages and may have relatively limited applications. The producers say their cement can be stronger, cheaper– and that’s in addition to being carbon negative.

One of the challenges of negative emissions is scale. Put simply, there’s too much carbon in the atmosphere and nowhere to put it. So, what if we took the most prolific building material on earth and transformed it from a carbon emitter to a carbon sink?

In this future, every footpath, road and building would be locking away carbon dioxide permanently. In this future, we don’t have to sequester carbon dioxide deep underground or perform expensive reactions to convert it to a solid. In this futre, we can simply continue building the infrastructure our growing population requires in order to flourish.

In the next 50-100 years, our civilization will undergo a period of unprecedented development. All large-scale energy generation will need to be replaced with low carbon alternatives to avoid catastrophic global warming. Infrastructure will need to be constructed for the additional 3 billion people who will call this planet home. Throughout this entire process, we will have a significant choice; either we can build this future on a foundation of polluting Portland cement, or on emissions-absorbing clean cement.

“We desperately need new infrastructure projects to transition to a carbon-neutral world, but in doing so we will have to emit a massive amount of carbon”

Franz-josef ulm, a professor of civil and environmental engineering at MIT.

This may seem far removed from the construction choices we make today but the choices we make now will have an exponential and lasting impact on the world we build tomorrow.

Wiley seeks innovative solutions and to understand the future of our industry and it’s value to our economy. As part of a path to a more sustainable future we believe Australia, like other markets will transition towards a low-carbon cement future.

If you want to explore green solutions for your operation across areas from low carbon cement to renewable energy, talk to us about your next project.




1. Beyond Zero Emissions. Rethinking Cement. Sydney : Beyond Zero Emissions, 2017.

2. Disabato, Mike. Are We Stuck With Cement. The Outline. [Online] June 28, 2018. 

3. Global Cement. Geopolymer concrete – A commercial reality. Global Cement. [Online] February 11, 2011. 


5. Solidia Technologies. Solidia Technologies. Solidia Technologies . [Online] 2018. 

6. Carbicrete. Carbicrete. Carbicrete. [Online] 2018.