Building materials from waste

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.