»BauCycle«

Project description „BauCycle“ for Verbund Materials Flyer

The German saying “as the sand of the sea”, which literally means “a ten a penny” has lost its validity. In many countries in the world the valuable resource sand is disappearing continuously. The main reason therefor is the boom construction sector which consumes vast quantities of concrete comprising mostly of sand and gravel. Every year around 40 billion tons of sand and gravel are consumed and on the other hand around five million tons of fine grained construction waste accrue in Germany every year. Until now this waste has been used as landfill or road construction material. Different Fraunhofer institutes (IBP, IML, UMSICHT, IOSB) have set themselves the task to process the construction waste in a way to generate a new sustainable material. The big goal of the project »BauCycle« is to reuse the construction waste below two millimetre particle size and to cover the whole value chain from developing innovative sorting processes and high-quality construction materials up to the development of a dynamic virtual commodity exchange.

Ideally four different pure mixtures can be reused for example for producing autoclaved aerated concrete (AAC). AAC is a lightweight construction material with excellent insulation properties, which is highly suitable for both load-bearing walls and insulation material in the interior. Experiments showed that mixtures of concrete and sand-lime bricks are suitable for the production of AAC and the best results could be generated with a mixture of 80 percent waste sand-lime bricks and 20 percent waste concrete.

The experiments also showed that a mixture of waste bricks and waste concrete can be used to produce geopolymers. Geopolymers are a cement-free construction material with similar characteristics to concrete regarding the strength and acid resistance. Furthermore geopolymers achieve a significantly better balance in terms of CO₂.

Besides the AAC samples of different composition the scientists could also develop a geopolymer-based façade plate and a sound-absorbing plate showing an open porosity structure with the same absorbing properties as products which are already available on the market.

Within the Project »BauCycle« Fraunhofer IBP is responsible for the utilisation of the sorted construction waste and in particular for the development of innovative and sustainable new materials, such as functional construction elements, sound-absorbing plates and cement-free binders.