In an earlier article devoted specifically to Rotterdam examples of the application of circular concrete, the fully circular concrete pits were mentioned as a typical Rotterdam initiative. The concrete bases for waste containers are now being used and put into use in Rotterdam, and in this article, we want to briefly discuss how these concrete bases are made and what is so special about their production.
A case study has been carried out regarding the tendering of these sub-basins. For the circular objectives, this case is a good example to map out how this process went and what lessons we can learn from it. Rotterdam buys concrete products in competition and awards based on ECI (Environmental Cost Indicator), without prescribing a technique or composition. This is different from the Urbcon approach, which is much more academic and careful. Although it is about non-constructive versus constructive concrete, in both cases it is important how you steer on environmental impact and market forces.
The supplier of the 100% circular concrete pits is Recycling Wegenbouwmaterialen Amsterdam (RWA), part of the Rutte group. This company does not use the smart crusher, but uses a different method, the Smart Liberator. As a result, the concrete is not 'crushed' but grinded. Gravel and cement are then released. 95% is reusable. This makes it an innovative concrete solution.
In short, this process makes new concrete from old concrete. Concrete rubble is dumped at the Rutte Group site as waste, this includes the old concrete pits that are released in Rotterdam. The concrete rubble is first broken up. This goes through the Smart Liberator, where the old concrete is returned to its original raw materials and separated into gravel, sand, and cement. These raw materials can then be used for new concrete, without wasting concrete during production. After all, it goes back to the storage bunker, after which it is used in the next production.
The concrete pit will be built at the same location where the old concrete is recycled. From the bunkers in the new, fully electric concrete plant, the concrete is measured to the nearest milligram. The kubel is cast in on an electric forklift, which transports the required amount of concrete to the mold.
This mold is filled with the raw materials of the old concrete together with new Eco2cem cement, a type of cement with a very small impact on the environment. Once the concrete dries, the mold is removed, and the new pit is ready. There are no residual flows of concrete; any residual material is immediately fed back into the process.
Solar panels and rainwater
The molds last more than 10 years and are stripped daily. The environmental costs resulting from this are so limited that they are left aside. Production is fully electric. The electricity is generated by more than 19,000 m² of solar panels at the Rutte Groep site. Since the concrete batching plant only collects 'raw materials' fully automated to the nearest milligram, there is no waste.
Finally, we mention another example of an innovative and circular application by the Rutte Group. The water with which the concrete is produced is rainwater. At the production location, all rainwater that falls on the 3-hectare roof is collected and stored in a large basin with space for 750,000 liters of water.