Closed-loop recycling of autoclaved aerated concrete

Xella Technology and Research, in a pilot study with the Hamburg-based Otto Dorner GmbH waste management company and the Ytong plant in Wedel, has been testing since 2013 how and in what amounts autoclaved aerated concrete (AAC) remains from demolished buildings or from waste disposal sites can be reused for new AAC production. The processing of the salvaged AAC-material should conform to the current technical standard: return of mixed demolition rubble, separation of contaminants (by metal separation, air density separation, swim-sink separation, manual resorting), pre-treatment in the crusher and sieves for predetermined grain size ranges. This is where grain sizes or moisture content, heavy metals, bitumen, sulphate or other impurities are analysed in detail. The sorting accuracy as performed by Otto Dorner has shown to be sufficient for reuse through reintroduction into AAC-production. Up to 15 % salvaged AAC prepared in such a manner can be effortlessly reused. A sample production of AAC quality grade P4-0.55 with granulated salvaged AAC in the Ytong plant in Wedel was successful.