R.E.J. van den Bogert
2021
In this study, we asked a practical question about a very common material: when a concrete building reaches the end of its first life, which circular routes genuinely lower environmental impact and which can realistically be used at scale? Concrete is indispensable to construction, but in the Netherlands it accounts for an estimated forty to sixty percent of the sector’s environmental impact, with cement responsible for much of that burden.
Our research grew out of SUPERLOCAL, where ten-storey apartment blocks were deconstructed to test new approaches to material reuse. We compared a conventional new-build baseline with five circular scenarios. Two kept existing material at a high level by cutting out and reusing whole apartment compartments or smaller slabs. Three turned demolition material into new products: prefabricated elements with recycled coarse aggregate, concrete poured on site with recycled aggregate and premanufactured BRX concrete bricks.
We calculated embodied energy and embodied carbon for every route using published data, project information from real demonstrators and established material databases. Reusing whole compartments or slabs offered the largest theoretical reductions—up to seventy percent in embodied energy and carbon compared with the baseline. But those routes also require specialist lifting, careful structural work, trustworthy information about the existing building and regulatory solutions that are not easy to secure.
The more promising options for broad use were therefore recycled-aggregate prefabrication, recycled concrete poured on site and BRX blocks. They can meet current rules more easily and still have room to improve through better production, smarter material use and future end-of-life planning. Circular concrete is not one technique; it is a set of routes with different impacts, limits and delivery conditions.
For us, the key lesson is that the highest calculated saving is not always the best choice for a real project. A credible circular transition needs methods that reduce impact while remaining safe, repeatable and buildable. Connecting calculations to on-the-ground experiments gave us a more grounded basis for deciding how yesterday’s concrete can become part of tomorrow’s city.