Construction and demolition waste, at 89 million tons, is the dominant type of waste in Germany in terms of quantity. These wastes are mainly recycled in earthworks and road construction. A major part of these studies deals with carefully graded concrete and has little to do with the processing and utilization practice. Fine-grained heterogeneous construction waste, such as masonry rubble in particular, cannot be cleanly sorted with the technology available today, resulting in interim storage or landfilling. For that reason, the idea of raw materials recycling was developed as an alternative approach. Here, masonry rubble containing sulfate can be accepted and processed. Apart from innovative lightweight aggregate, this process produces gypsum from flue-gas desulfurization.
The energy consumption in lightweight granule production from masonry rubble was calculated based on thermodynamic data. Another major advantage is the low consumption of resources. Non-recoverable waste materials, for example, are transformed into high-quality products, reducing the burden on landfills. The problems of the recycling industry in transforming fine fractions and gypsum-based demolition materials into products of higher quality can be solved, thereby preserving non-renewable raw material resources such as expandable clays, pumice and gypsums. The lightweight granules can be used as lightweight aggregate in the concrete industry as plant substrate and filter material.