Hey Reader,

Concrete is one of the most used materials on earth.

It’s everywhere.

In our houses, offices, roads, bridges.

In Belgium alone, around 12 million cubic meters of ready-mix concrete are produced every year.

In the Netherlands, it’s around 14 million cubic meters. In France 40. In Germany 50.

Hard to visualize? I get it, for me as well. I’m not a swimmer, so I won’t bother you with these “Olympic swimming pool” comparisons.

For Belgium, it means 7 bathtubs full of concrete. Per inhabitant. Per year.

These huge volumes are why concrete keeps coming back in sustainability discussions. And why we should have a closer look.

Bonus: Stick with me until the end to get to know me better.

Where does the environmental impact really come from?

Let’s zoom out and take a look at how concrete is produced.

You need:

• Cement: the glue
• Aggregates: sand and gravel
• Water: you know what water is
• Admixtures: chemicals that make concrete flow faster or slower, make it more frost-resistant,…

While aggregates make up most of the weight, they contribute only a small part of the carbon footprint.

Cement is a different story.

At a global level, cement is responsible for around 7% of global CO₂ emissions.

That alone explains why concrete keeps appearing in climate discussions. Often from a tunnel vision on carbon.

In this edition, I want to zoom in on a different dimension: circularity.

Concrete is one of the most used materials globally.

Every year, huge amounts of sand, gravel and crushed stone are extracted, mixed into buildings, and later returned as demolition waste.

Today, most demolished concrete is crushed and reused as foundation material, especially under roads. That is recycling, but it’s low-value recycling.

If we want to become circular, at the end of life, concrete needs to become concrete again.

Raw materials and biodiversity

A typical cubic meter of concrete weighs about 2,400 kg.

Roughly 1,800 kg of that is sand and gravel.

Those materials come from somewhere:

• Quarries (aka mining)
• Rivers
• Sea

You probably have already seen pictures of quarries.

Explosions, massive excavators and gigantic trucks are bringing the mined raw materials up from deep pits.

Large areas of land are transformed and ecosystems are disrupted.

The sheer quantity of primary raw materials creates real pressure on land-use and biodiversity.

I’m not trying to shame mining companies. We’re all in this.

That’s the whole idea behind knowing what happens in your value chain. If you use truck loads of concrete, you can’t close your eyes for where the materials come from.

Even the Belgian association of ready-mix concrete (Fedbeton) starts bringing up the biodiversity impact on their presentations. It’s mostly one small slide, but hey, we’re getting there!

You’ve probably heard warnings that we might “run out of sand”.

Sand is a finite resource, even if we can’t image this right now.

Yes, there is plenty of sand in deserts but that sand is too round. It doesn’t bind. You can’t use it for concrete.

And it’s not just aggregates: the limestone needed for cement also comes from mining. In that sense, almost everything in concrete starts in the ground.

Reducing the use of virgin materials by reusing what we already have is not only a circularity matter but also a way to put less stress on nature.

What circular concrete wants to achieve

Circular concrete focuses on two things at once:

• Lowering the cement impact where possible
• Replacing virgin aggregates with recycled ones

I’ll go deeper into cement and its decarbonisation possibilities in a next edition.

The second part sounds simple. Demolish a building, crush the concrete, reuse the sand and gravel.

But it’s not that easy.

Concrete quality depends on consistent input materials. Demolition waste is often mixed: bricks, soil, plaster.

Producing recycled aggregates that meet the right quality standards requires careful sorting and processing.

What is possible today?

Concrete is heavily regulated. Structures are expected to last for decades. Failure is not an option.

In Belgium, concrete products are typically certified under BENOR. In the Netherlands, Kiwa / KOMO certification plays a similar role. And there are European standards as well.

The good news: many concrete mixes allow a percentage of recycled gravel depending on strength class and where it is used.

But it stays limited. And the frameworks evolve slowly to make it happen on scale.

Until now, it’s not possible to reuse sand in Belgium. Currently, there is a draft for an update of the concrete norm which will allow recycled sand under strict conditions.

So that’s it? We can’t go further than what those norms say?

It’s possible. Today. No need to shelve the ambition!

The Netherlands have a lot of experience with project-based concrete tests, allowing controlled deviations for specific use cases. That makes it easier to experiment at project level, without waiting for full product certification.

In Belgium, similar innovation tracks are now starting up as well.

Additional testing, proper documentation and approval by the client, engineer and contractor makes it possible to deviate from the norm.

Is circular concrete even available?

This is the part most people underestimate.

In Flanders, around 95% of stony construction waste is recycled.

Unfortunately, most of that material ends up in low-value applications: foundations, road bases, fill material.

Very little is recycled into high-quality aggregates that can be used for structural concrete again. In Belgium these are called A+ granulates.

In Belgium and the Netherlands there are only a number of concrete producers that offer poured concrete with recycled granulates.

Mostly these have their own concrete crushing installations.

As the limited available amount is used directly, it’s almost impossible to buy recycled granulates as a separate product.

And why is that? Not enough trust by engineers and business as usual technical specifications that don’t allow mixed rubble for foundations.

What can you do to make circular concrete happen

There is already plenty of room to move today:

• Use existing overviews to understand what is possible per strength and exposure class
• Buy concrete with the maximum allowed recycled content
• Are you a building owner whose building is deconstructed? Oblige that your waste is being recycled into high-quality granulates
• Legislation: make it mandatory for high-quality concrete to be recycled into granulates for reuse in concrete.
• Innovation tracks and project-based tests can help build confidence for producers, contractors and clients.

Don’t wait until circular concrete is magically available at scale with the perfect norms.

Go for it now. No need to be afraid.

Have you used concrete with recycled aggregates before?

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This was the sixth edition of the Building Beyond BAU newsletter and I hope that you enjoyed it Reader.

I thought it was time to get to know each other a bit better.

And what better way to judge someone than by their music taste?

I'm aware that this could go wrong, but you’ve already been patient with all the gifs ;-)

No worries, I'll spare you my "normal" taste of music. Instead, I’ll share the playlist I listen to while writing this newsletter.​

Mostly jazzy stuff that helps me focus, either early in the morning or when my beautiful wife is watching “2 Broke Girls” next to me.

Always curious for any type of recommendations!

Enjoy the rest of this beautiful Sunday. Have a great week!

Best,

Simon