New method to transform construction waste into useful materials

A group of German researchers has found a way to manipulate construction waste by turning them into new materials.

Construction industry is highly developed in Germany, a country that handles about 100 billion metric tons of material waste. Scientists from 4 Fraunhofer Institutes are now investigating the potential of recycling fine-grained building rubble.

A method, called the BauCycle process, which separates the rubble's components using an opto-pneumatic detector has been developed. Under certain conditions, BauCycle can process about 1.5 metric tons per hour. Fine fractions are distinguished by color, brightness and chemical procedures. "The waste components are placed on a conveyor belt that transports them past an infrared camera equipped with special filters to detect the various fine fractions. The particles drop off the end of the belt in free fall, past nozzles that shoot the main components into different containers with targeted blasts of compressed air," says Fraunhofer IBP scientist Dr. Volker Thome, the project's manager.

The purpose of the project is to create a component deposit made of construction waste that could be utilized in various applications and be recycled into construction industry. For example, geopolymers, a building material with lower carbon footprint than concrete, can be produced by mixing bricks and such components. Additionally, aerated concrete, a lightweight, precast, foam concrete material with good thermal insulation can also be produced using those separated components.

Business plans to invest in a recycling material market still lack confidence but efforts are made to improve the situation. "Recycled products have yet to be sold on established markets. There is a lack of confidence in and knowledge of these secondary raw materials. We want to close this gap with a commodities exchange," Dr. Thome stated.