Resource conservation potentials through recycling aggregates
Building without concrete is difficult to imagine nowadays, because the proportion of concrete in residential buildings is nowadays higher than 50%, and often even as high as 90% for commercial high-rise buildings.1 This leads to the fact that 42 million cubic metres or 100 million tonnes of ready-mixed concrete was used in construction in Germany during 2010, and the concrete used for precast sections still needs to be added to this.2
On the way to a national sustainability strategy with recycling material
This represents a considerable material flow which the German government's national sustainability strategy wants to see reduced. One of the core objectives of this strategy is doubling raw materials productivity by 2020 over 1994.3 Since raw material productivity is defined as a quotient of the gross domestic product in Euros through the use of abiotic raw materials in tonnes, the aim is to reduce the raw material requirements for sand, gravel and natural stone. The huge mass flows in the construction industry, and that of the mineral aggregates during concrete manufacture in this special case, play a major role. The latter represent the main component in concrete as an additive with around 80% of the mass, and can be partially produced through the use of recycling aggregates.
The use of recycling material has a double positive effect in matters of sustainability:
- Secondary utilisation of materials prevents additional raw material extraction and therefore plays a role in increasing raw materials productivity through reduction of raw material usage
- Land acreage used for extraction of mineral raw materials from near-surface deposits is reduced
The fact that consumption for the extraction of mineral building materials is considerable is shown by a figure originating from 2008. At the time, an estimated 3.8 hectares per day were being made use of.4 A comparison with the aims of the national sustainability strategy, which aims to reduce acreage use for residential and traffic areas to 30 ha per day by 2020, makes the magnitude of the area used up in association with raw material extraction very clear. Extracting gravel using the wet extraction method, i.e. below groundwater level, also damages the groundwater stratum.
1 Ifeu-Institut, Öko-Institut, iöw gGmbH, Kommunikation- und Konfliktberatung Gerhard Jakubowski, 2008: Steigerung von Akzeptanz und Einsatz mineralischer Sekundärrohstoffe unter Berücksichtigung schutzgutbezogener und anwendungsbezogener Anforderungen, des potenziellen, volkswirtschaftlichen Nutzens sowie branchenbezogener, ökonomischer Anreizinstrumente, UFO-Plan-Vorhaben (FKZ 205 33 313)
2 ATEC Business Information GmbH (Hrsg.): Recycling-Almanach 2012, Imageproblem im Hochbau, S. 112 ff.
3 Nationale Nachhaltigkeitsstrategie, 2002
4 Keßler, H., 2011: Urban Mining – Ressourcenschonungspotenziale einer hochwertigen Nutzung des anthropogenen Lagers im Gebäudebestand, Tagungsband zum 23. Kasseler Abfall- und Bioenergieforum, Hrsg. Witzenhausen-Institut