Worldwide, it is estimated that more than 25 billion tonnes of concrete are used annually. The environmental impact of concrete production is therefore also great. For the production of concrete, in addition to granulate, cement is needed and the production of cement is not only energy-intensive (ovens up to 1450 ° C), but also ensures high CO2 emissions.
In addition, not only new concrete is produced, but also a large amount of building and demolition waste is released each year. In total, 2.5 billion tonnes of waste was generated in Europe in 2012, of which 34% is accounted for by construction and demolition waste. Figures for Flanders and the Netherlands speak of an annual amount of concrete rubble released from 7 Mton and 20 Mt.
Although efforts are being made in many countries to recycle this construction and demolition waste as a construction product, worldwide landfilling is still often accepted as the solution for this waste stream. In Flanders and the Netherlands, concrete rubble is mainly applied at low value (downcycling), i.e. as broken granulate in foundation layers, surface pavements or for additions. In addition, the fine fraction (cement) released during forced separation is today a problem waste that can hardly be valorised.
The main reason for the low-grade reuse of concrete granules is that in classic crushing plants the hydrated cement is not separated from the granulate (sand and stones), resulting in a porous material of lower and less constant quality. With the aid of new, innovative separation techniques, the different fractions of concrete (sand, granulates and cement) can be better separated from each other, which should allow a high-quality application of the various fractions. In this project two innovative technologies are investigated: microwave treatment of concrete and the Smart Crusher (Slimbreker) technology of SCC B.V.. Recent research has shown that the better separation between cement, sand and gravel ensures that:
i) the granulate and sand fraction have similar properties to the constituent natural granules of the concrete, so that these granules can be used again in the same concrete applications and in a high-quality manner.
ii) the reclaimed cement fraction can be reused as a binding agent after thermal treatment. For the use of the fine fraction as an alternative binder, two runs are possible:
1) The obtained recycling material functions as cement provided alkali activation after dehydration (<450 ° C).
2) The obtained recycling material acts as cement substitute due to its binding properties after dehydration and calcination (> 450 ° C).
This also opens the door to a new energy-efficient way of cement recycling. The recycling of the fine fraction as a binder will reduce the CO2 emissions / environmental impact compared to cement because i) no CaCO3 is used, such as for cement, ii) is operated at a lower temperature, iii) green electricity can be used instead of fossil fuels, iv) reduces transport and v) natural resources are not further depleted.
The proposed innovation offers a solution for the growing number of customers looking for high-quality (concrete) products with the lowest possible environmental impact. After all, this project must allow the production of high-quality concrete products based on both recycled granulate and an alternative recycled binder.
Short titleBnB
Effective start/end date1/03/1828/02/21

    Research areas

  • Beton

ID: 37527866