Christian M. 6 min read

Cleancrete: Is low-carbon concrete a game-changer?

Concrete is the most ubiquitous man-made material in the world due to its simplicity, strength and durability, and its consumption as a building material is second only to the human consumption of water.

Cement is a key component of concrete, but its production process is carbon-intensive, contributing 8% of global carbon emissions. This makes the concrete/cement industry a cradle for disruption, and disruption is what we are seeing.

In this article, we cover Cleancrete: a solution pioneered in Switzerland that entirely replaces the need for cement in concrete making.

How is cement produced at present?
How is concrete made?
The disruptor: Oxara Cleancrete
How is this Cleancrete made?
Why is the use of natural earth materials so valuable?
What are the challenges facing Cleancrete?
Is Cleancrete disrupting the construction industry?
Are there other alternatives to green concrete?

How is cement produced at present?

The most common type of cement is Ordinary Portland Cement (OPC), which is made by heating up limestone and other raw materials to 1,450C in a massive kiln in a process called calcination that emits astronomical amounts of CO2.

On top of this, the high temperatures required are achieved by burning fossil fuels like petroleum coke and coal to produce a powerful luminous flame.

The chemical process of calcination emits 60% of the CO2, while the other 40% comes from the consumption of fossil fuels to heat up the kiln. Together, and including the associated emissions from the likes of quarrying and transportation, the cement industry produces 8% of global CO2 emissions, almost as much as the entire emissions of China.

And in terms of other environmental effects, some heavy metals are emitted in the process of calcination, as well as dust and noise, affecting the local environment.

How is concrete made?

Concrete has become the most popular building material on Earth because of its simplicity, durability, strength and range of applications.

Concrete may be made to meet a wide range of specifications by mixing different proportions of:

Cement
Chemical additives
Sand/gravel
Water.

High-quality concrete can be made on an industrial scale to meet the structural needs of nuclear reactors or hydroelectric dams, while home-mixed concrete can be used by DIY enthusiasts to fix simple structures like garden walls.

The disruptor: Oxara Cleancrete

Taking inspiration from Togolese earth-buildings Oxara has developed a new way to create a concrete-like material without the need for cement, using instead naturally occurring clay and sand.

The process of making the Oxara Cleancrete is significantly cheaper and cleaner than that of typical concrete, as it does not require the energy input cement-making requires.

Oxara claims that the process is 2.5x cheaper while reducing emissions by 90%, which is significant considering that it plans to disrupt the carbon-intensive construction industry.

How is this Cleancrete made?

Like concrete, Cleancrete is made by mixing together several materials in the prescribed proportions:

A non-toxic powder additive (the key spice!)
A range of earth materials (clays, silts, sands, gravel)
Water

The key difference is that the input materials have a significantly improved environmental footprint.

Instead of cement and chemicals, the non-toxic additive that is derived from mineral salts. The natural occurring additive binds materials together and gives structural integrity to the Cleancrete.

And like concrete, it takes between 24-48 hours to cure.

Why is the use of earth materials so valuable?

Another key advantage of Cleancrete is its tolerance for a large range of earth materials compared to normal concrete, which requires the procurement of high-quality sand/gravel.

This means that Cleancrete can source a large proportion of its ingredients from the construction site itself, and often at no additional cost since the mass removal of soils is often part of any project (i.e. to make space for basements, underground parking, foundations, etc.).

Engineers can directly re-use a proportion of the removed, non-polluted ‘waste’ soil that constitutes approximately 76% of construction waste in the EU.

On top of this, natural soil often contains fine materials like clays and silts that come with the added benefit of having thermal properties that are good for buildings.

The result is properties that remain cooler in summer and warmer in winter, further reducing the long-term energy usage of businesses that require heating or A/C.

What are the challenges facing Cleancrete?

Like any new, disruptive technology, Oxara’s Cleancrete also faces many challenges.

Firstly, Cleancrete has one-sixth of the strength of typical concrete, which means that its safe use is limited to smaller structures, like two-story buildings.

Being a new material in the market means it needs to be validated in the real world to become trusted by engineers, architects, regulators and other stakeholders within a stubbornly conservative construction industry.

Is Cleancrete disrupting the construction industry?

As countries are increasingly under pressure to reach net-zero by 2050, pressure is mounting to adopt new solutions, and Cleancrete’s environmental advantages in this area are clear.

Its striking similarities to the process of concrete mixing also make it easily adaptable to current infrastructure, and in fact, the team have successfully produced a batch of Cleancrete at an industrial concrete factory in Switzerland without having to adapt any of the machinery or process.

This is key because it means that very little investment is needed to be implemented at scale and replace a portion of the carbon-intensive concrete market.

A new apartment block in Zurich is already trialling Cleancrete, which would deliver appropriate strength while giving the necessary thermal properties to reduce the need for heating for a Swiss winter.

All being well, there is no reason to believe Swiss regulators would give this material a no-go if the trials are successful, and once this happens, it would make it easier for other countries to adapt, especially considering Swiss regulation is stricter than most.

And of course, the ‘Made in Switzerland’ or at least, ‘Trialled and tested in Switzerland’ is a very good brand.

Are there other alternatives to green concrete?

Much research is being directed at reducing the emissions of cement-making and at reducing its use as a construction material.

For example, a lot of research is focused on adapting green hydrogen to heavy industry as it can be burnt to create large amounts of heat energy to power the cement kilns and significantly reduce 40% of the industry’s emissions.

Other initiatives are exploring different mixtures that reduce the amount of cement needed to make concrete, while others are exploring the use of waste material from other industries to replace some of the ingredients, like sand and chemical additives.

Final thoughts

It’s very exciting to see very simple yet elegant solutions like Cleancrete disrupting old industries. It goes to show that saving the planet is often not a matter of developing NASA-worthy technologies but of keeping an open mind.

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