To create a more circular economy, recycled building materials present a big opportunity. But there’s a snag: “We have to be sure that recycled materials offer the same performance as new ones,” explains Xavier Guillot, Head of Product Certification and Standards, LafargeHolcim France: “For example the coarser parts of recycled aggregates can be more easily reused in concrete, but finer ones like sand are more porous and could potentially lower the properties of the final product.”
This is where FastCarb comes in. FastCarb is a collaborative research and development project sponsored by the French government with 22 industrial and academic players in which LafargeHolcim is playing a key role. Xavier explains: “The project is part of the country’s quest to achieve carbon neutrality and create an economy that is truly circular.”
The overall objective of FastCarb is twofold. For one it aims to improve the properties of recycled aggregates so they can find more applications, be used more widely and become more marketable. This could be facilitated via a process called mineral carbonation, where CO2 is combined with the calcium present in the cement paste that covers the aggregates. This results in closing the pores so that less water and admixtures are used in the concrete and the properties are improved. The second part relates to the reuse of carbon. “The CO2 can be sequestered from any nearby industrial source, for example a cement, coal, or steel plant,” Xavier explains.
The project will be completed in 2021. The lab results from the carbonation reactor at LafargeHolcim’s Val d’Azergues cement plant so far are promising. As concrete throughout its life cycle soaks up 15% of CO2 emitted during the cement calcination process, first tests are showing that FastCarb can help achieve an additional 30% reabsorption within just a few hours instead of decades. If successful, FastCarb could represent a significant breakthrough in reinventing construction to make it greener and smarter for all.