Recarbonate to create 100% recycled concrete
Construction and demolition waste can already be used to create new low-carbon building materials - particularly for aggregates, a key ingredient of concrete. But this recycled rubble made from old concrete is sometimes more porous. It means that it’s typically used for applications in road sub-bases rather than concrete.
Our innovation teams set out to produce concrete made from 100% recarbonated recycled rubble. That’s creating concrete that is fully recycled, high performance and low carbon. It literally paves the way to truly circular concrete!
Recarbonation to make high-performance concrete with FastCarb
We’re already well on the way to making this happen with FastCarb. It’s a technology that creates improved recycled aggregates by adding untreated diluted CO2 to the old concrete.
The good thing is that the CO2 comes from our own industrial processes, captured from the flue-stack. The CO2 then reacts with the old concrete to create a coating that effectively seals the rubble. The result - high-performance 100% recycled aggregates - opens up a world of potential to be used in other applications.
“The project is part of our quest to achieve carbon neutrality and create an economy that is truly circular”, says Xavier Guillot, Head of Product Certification and Standards, Holcim France. “The really smart part is that the concrete absorbs the CO2 as part of the process, locking it inside the final product and helping to prevent its release into the atmosphere. The CO2 can be sequestered from any nearby industrial source, for example, a cement, coal, or steel plant. This means that cement plants could actively reduce their own carbon emissions as well. It’s a great example of the circular economy in practice.”
FastCarb is the outcome of a project partially funded by the French government. The technology has been created by Holcim and 22 academic and industrial partners, including Holcim. In 2021, the pilot has been taken to the industrial testing stage at our site in Val d’Azergues, France with some great results: we discovered that the carbon footprint of concrete made with 100% carbonated recycled rubble could be reduced by up to 25%.
We’re already exploring other areas of recarbonation. In Austria, a similar technology to FastCarb is being used in R&D where we grind old concrete in our mills while reinjecting it with untreated CO2 from our own plant. We’re hoping for more promising results.