"Staubgold" - Turning dust into gold
Porous building materials for sound and thermal insulation made of fine-grained concrete, construction and demolition waste
With great force the demolition ball breaks a massive hole into the wall of the dilapidated building – it cracks, dust swirls up. Such a demolition is inevitably accompanied by a lot of building waste: In Baden-Wuerttemberg, concrete, construction and demolition waste annually amounts to around 36 million tons, 90% of which are recycled. The remaining 10% mainly consist of fine-grained material which is disposed of in landfill. Scientists of the Fraunhofer IBP are working on solutions to convert this fine-grained waste into sustainable functional building material to be used for sound and thermal insulation purposes, thus feeding it back into the material cycle. In other words: The scientists turn “dust” into “gold”.
Usually, construction and demolition waste is ground, then a foaming agent is added to the material which is thermally bloated to gain porous granules – a very energy-intensive process. The situation is different, however, for the so-called “build-up granulation”. The Fraunhofer experts use this type of granulation to produce micro-porous granules from fine-grained waste which they turn into panel form by help of inorganic binders - and completely without using any additional thermal energy. As an alternative procedure the scientists also apply foaming: Using the available scope the manufacturing of micro-porous granules is offering, the scientists optimize the microstructure of the granules such that the resulting material reaches competitive values for sound absorption and thermal insulation. With good results: The first foamed micro-porous test specimen are mechanically stable and show a promising good sound absorption.
The scientists also focus on the environmental compatibility: They investigate both the fine-grained waste and the new building material with regard to their environmental sustainability. If there are pollutants accumulated in the building waste, the experts can detect them and thus avoid their release. In addition, the Fraunhofer IBP deals with the sustainability impact assessment: Which are the benefits of the procedure, from an ecological, economic or sociocultural point of view? In answering this question the scientists will have taken a decisive step towards a further industrial development.