No abstract

In Germany, about 60 million tons of demolition waste are generated annually. Approximately 70% of the demolition waste is currently recycled. Most recycling applications, for example in roadbed substructures, can be seen as a kind of downcycling. However, there are also some high-level applications for demolition waste. For instance, crushed and sieved concrete demolition waste can be used as concrete aggregate instead of natural materials. Depending on the crushing process, about a third of the broken concrete is currently concrete sand. At present, concrete sand fraction (0-4 mm) is rarely reused as a concrete aggregate. This is due to the fact that some important characteristics of crushed concrete sand are different from those of natural sand. As a result, it does not reach the standards required for aggregates. Concrete containing such aggregate is of lower quality than concrete made of natural aggregate. This paper describes an experimental investigation on the treatment of concrete sand gained from demolition waste by wet processing using a jig whereby the sand is separated by grain size and, more importantly, by density. Concrete produced with concrete sand which has been treated in this manner should have the same quality as concrete prepared with natural aggregate. Recycled sand used as aggregate substitutes natural resources and avoids disposal of waste. It has all the characteristics of an Ecomaterial.

Gypsum is widely used in the construction sector, and its worldwide consumption has been increasing for several decades. Depending on the lifetime of the used gypsum products, an increase of gypsum in construction and demolition waste follows. Especially against the background of a circular economy, the recycling of waste gypsum is of growing importance. However, the use of recycled gypsum only makes sense if it is environmentally friendly. Therefore, an evaluation of the environmental impacts of industrial-scale processing for the recycling of post-consumer gypsum waste was conducted. The evaluation was performed with an established life cycle assessment software. Original data provided by the industry and complementary data from a database for life cycle assessments were used for the calculations. Two scenarios for recycled gypsum with different transportation distances were calculated. These results were compared with the results of the environmental evaluation of gypsum derived from coal-fired power plants (FGD gypsum) and natural gypsum. The results showed that the utilization of recycled gypsum can be environmentally advantageous compared to the use of natural gypsum or FGD gypsum, especially in the impact categories of land transformation and resource consumption (abiotic depletion potential). For most environmental impact categories, the specific transportation distances have a strong influence.