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ENSUBA–A new method for solving the gypsum problem in waste autoclaved aerated concrete
Author(s) -
Liesch AnnaLena,
Thome Volker,
Dittrich Sebastian
Publication year - 2018
Publication title -
ce/papers
Language(s) - English
Resource type - Journals
ISSN - 2509-7075
DOI - 10.1002/cepa.886
Subject(s) - gypsum , autoclaved aerated concrete , anhydrite , ettringite , waste management , demolition waste , shrinkage , reuse , demolition , building material , environmental science , materials science , engineering , civil engineering , cement , composite material , portland cement
According to a previous study, the existing building stock in Germany contains up to 10% of gypsum building material, which is integrated in walls, ceilings, and floors. After the demolition of these buildings and their reuse in recycling building material (RC building materials), gypsum causes severe problems, such as sulfate attack and the corresponding concrete damages. Due to these problems the majority of the gypsum‐containing demolition waste is deposited in landfill sites. The other option – recycling the autoclaved aerated concrete (AAC) – is very difficult: according to the current technological standards and a previous study, almost all AAC formulations contain a certain amount of sulfate mineral phases in the form of gypsum or anhydrite. The use of the sulfate minerals is necessary for production reasons and to meet mechanical material requirements such as compressive strength and shrinkage. In this work a method known from the conservation and restoration field where ammonium carbonate compresses are used to remove gypsum from paintings and frescos is modified and applied to AAC recycling. It could be shown that the calcium sulfate phases can be removed to an amount, which allows to use AAC as an RC material or to make deposition much easier.