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Current situation, challenges and pioneer works

Circular economy of autoclaved aerated concrete

In the present paper, a reuse strategy for Autoclaved Aerated Concrete (AAC) demolition waste into the ongoing production of AAC is described. The challenge is huge: The decisive factor for successful recycling is primarily the quality of the AAC recyclate. This must be carefully analyzed before the material is reintroduced into the production cycle. A collaborative pilot project between Xella and the Otto Dörner Entsorgung GmbH has shown that from the point of view of process and materials technology, production of high-quality AAC is even possible under utilization of crushed AAC from demolition. For construction and demolition waste (CDW) from AAC, disposal is ensured in Germany with landfill class I (“Non-hazardous mineral waste”). In order to save disposal costs, Xella offers to take back unmixed cutting waste, which arises in the course of new building or refurbishment. This activity is Xella’s preparation for the European Waste Framework Directive, pursuant to which at least 70 percent of all construction and demolition waste must be recycled after 2020. It must furthermore be expected that building material manufacturers will be faced with a takeback obligation for building materials once this directive enters into effect. An innovative new calcium silicate product that contains an essential amount of re-used AAC was recently launched at the leading fair BAU 2019 in Munich. Xellas long-term aim is a closed recycling loop for AAC. And this new product is a big step forward to this ambitious goal.