About the project

In the BnB project, prefabricated building elements will be developed with a high content of recycled construction and demolition waste (> 30%). The intention is to use advanced breaking and sorting technology (microwaves) to produce pure raw materials that can be reused as binders, fillers or aggregates for prefabricated building elements.

It is estimated that more than 25 billion tonnes of concrete are used worldwide every year. The environmental impact of concrete production is therefore also large. To produce concrete, in addition to aggregates, cement is required. The production of cement is not only energy-intensive (furnaces up to 1450 ° C), but also generates high CO2 emissions.

875 million tonnes of construction and demolition waste in Europe

In addition to the production of new concrete, large amounts of construction and demolition waste are created every year. A total of 2.5 billion tonnes of waste was generated in Europe in 2012, of which 34% (875 Mton) is construction and demolition waste. In Flanders and the Netherlands the figures for the annual amount of concrete rubble produced are 7 Mton and 20 Mton respectively.

Although efforts are being made in many countries to recycle construction and demolition waste as a construction product, landfilling is often still accepted as the solution for this waste stream. In Flanders and the Netherlands, concrete rubble is mainly applied in low quality applications (downcycling), for example as broken granular to fill in foundation layers, surface pavements or for fillers. Additionally, the fine fraction (cement) that is released during thorough separation is currently a problem waste which is difficult to recover.

BnB: investigation of two innovative separation technologies

Two innovative technologies are investigated in this project: microwave treatment of concrete and the Smart Crusher (Slimbreker) technology of SCC B.V.. Recent research has shown that improved separation between cement, sand and gravel ensures that:

  • the gravel and sand fractions have similar properties to the constituent natural aggregates of concrete, so that these aggregates can be reused in the same high-quality concrete applications.
  • the recovered cement fraction can be reused as a binder after heat treatment. Two routes are possible for using the fine fraction as an alternative binder:
    • The recycled material obtained acts as a cement provided alkali activation after dehydration (<450 ° C).
    • The recycled material obtained acts as a cement substitute due to its binding properties after dehydration and calcination (> 450 ° C).
    • This also opens the door to a new, more energy-efficient way of producing cement. By recycling the fine fraction as a binder, the CO2 emission / environmental impact will decrease considerably because i) unlike virgin cement, no CaCO3 is used and decarbonated ii) lower temperatures of formation are employed.
  • transport is reduced.
  • natural resources are not depleted any further.

High-quality concrete products with the lowest possible environmental impact

The proposed innovation therefore offers a solution for the growing number of customers who are looking for high-quality (concrete) products with the lowest possible environmental impact. This project will allow for the production of high-quality concrete products based on both recycled aggregates and an alternative recycled binder.

Furthermore, textile reinforcement in concrete can lead to further innovation. The use of textile reinforcement makes it possible to produce thinner elements, which leads to a reduced total material consumption, but also the problem of reinforcement corrosion is eliminated. Moreover, by using innovative separation technologies, the recycling of such elements is no longer a problem.