One more step to take toward fully recycling concrete

Recycling of concrete is already largely possible for Renewi. Gravel and sand are already recovered from it, and its quality is high. 'But,' says Jan-Pedro Vis, Director Product Management & Innovation at Renewi, 'the biggest CO2 -profit is in the next step, the filler as a cement substitute.' They want to take that step at Renewi in the near future. But for that, clients are badly needed.

When it comes to circularity in construction, concrete is the biggest challenge. That's why 2018 also saw the concrete agreement concluded between manufacturers, builders and governments, stating that by 2030 concrete should be completely circular. 'That's the ambition,' says Vis about it. 'But getting that done, you need the whole chain for that.'

RWS stuck its neck out

Vis sees a big role for clients. 'The client wants the demolition of a building and then the construction of a new one. In doing so, that client must have the ambition to reuse the recycled material from the old building in the new one.'

That is why Vis is full of praise for Rijkswaterstaat. 'They really stuck their necks out when demolishing two viaducts along the A9. Because the easiest way to demolish is to crush it with a mobile crusher, where the components are not separated. Only then the recycling value is low. That material is used as a foundation under roads. RWS has given us the opportunity to recycle at a high value by separating the components during demolition. This creates pure concrete rubble that we can recycle at a high value and that can be used again in concrete in RWS projects.'

The constituents of concrete

Besides water, concrete consists of three components. Gravel, sand and cement. Those first two components, gravel and sand, are now recovered from concrete rubble by Renewi. "We turn that into recycled material that the client says, "Wow, that's quality and sustainable!"

Investing in machinery

The next goal, of course, is to make concrete from the recycled material, and for that they want to work with concrete producers at Renewi on circular concrete development. But the demand from the clients has to be there.' Because on that basis we can start investing in developing machines and production lines for filler as a cement substitute.'

The RWS case should make it easier for clients to make that choice, Vis believes. 'It is a milestone and a source of inspiration for future projects in the Netherlands and it underlines how shared responsibility can accelerate the transition to a circular economy.'

The filler is the final hurdle

With that support, the final hurdle for fully recyclable concrete should also be cleared; the filler as a cement substitute. It is very important that this step is made, argues Vis. 'Because then the CO2 -counter is really running. The big profit is in the filler, and we want to take that step together with the clients.'

At Renewi, they are doing a lot to make construction more circular, says Vis. 'The construction site is a treasure trove of valuable raw materials. We support in a waste-free construction site by critically examining what waste comes in and by sorting the waste on site. As a result, we minimize the amount of waste and maximize the preservation of valuable raw materials. For example, old wood is reused for biomaterials and we make boards from tomato stems. We have a very broad portfolio of circular materials. But fully recycling concrete is really a very big step. We want to make that happen. But for that we also need the clients, who hold the key now.'

Pedro Vis at BouwBeurs 2025

If you want a detailed explanation of Renewi and RWS's project by Jan-Pedro Vis, come to BouwBeurs 2025, which will be held from Feb. 3 to 7 at Jaarbeurs Utrecht. There, Vis will elaborate on the challenges involved in recycling concrete in a presentation.