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- Bauschuttaufbereitung (4) (entfernen)
Die Qualität von rezyklierten Gesteinskörnungen muss nicht nur bautechnischen Anforderungen und rechtlich verbindlichen Umweltstandards genügen, sondern ihr Einsatz in der Betonherstellung wird auch vor dem Hintergrund der Leitlinien der Nachhaltigkeit bewertet. Für die Gewinnung von rezyklierten Gesteinskörnungen bedeutet dies, dass sowohl bei den Abbrucharbeiten als auch bei der Bauschuttaufbereitung darauf geachtet werden muss, dass die gewählten Verfahren nicht nur ökonomischen Kriterien genügen müssen, sondern auch keine nachteiligen ökologischen oder sozialen Auswirkungen haben dürfen.
In verschiedenen Forschungsprojekten konnte durch ökobilanzielle Bewertungen von einzelnen Verfahren und Verfahrensabläufen gezeigt werden, dass rezyklierte Gesteinskörnungen aus Altbeton unter bestimmten Rahmenbedingungen umweltverträglich gewonnen werden können und ihre Nutzung durch die Substitution von Natursteinkörnungen sowohl zur Schonung von natürlichen Ressourcen als auch zu einer Reduzierung von Umweltbelastungen beitragen kann.
Concrete is one of the most widely used construction materials and, accordingly, the concrete industry is an important stakeholder in the field of sustainable construction. Therefore various approaches have been implemented to increase the sustainability of concrete. Besides reducing CO2-emissions during cement production, increasing the energy efficiency of buildings and extending their life span, the end-of-life performance of concrete is also an essential aspect of sustainability. Reusing concrete as a secondary building material meets the requirements of sustainability in several ways: the extended time availability of primary raw materials and, thereby, the protection of natural resources as well as conserving landfill site. Furthermore, the production of recycled concrete aggregates (RCA) is a good example for closed-loop recycling.
However, regarding the use of RCA as a substitute for natural aggregates in concrete, attention must be paid to all issues of sustainability: this means that environmental, economic and social aspects have to be considered. Since RCA generally have inferior building material properties, such as higher porosity and lower density, the implementation of closed-loop recycling of concrete only makes sense if the technical quality assurance is secured. This paper focusses on the implementation of techniques for the deconstruction/demolition of buildings and the subsequent treatment of concrete rubble in order to improve the building material properties of RCA with regard to the requirements of sustainability and also technical rules and standards.
Due to the large quantities of construction and demolition waste (CDW) in Europe, its reuse or recycling is of particular importance. Although several countries already recycle high amounts of CDW, the use as secondary raw materials is often limited by inferior building material properties. Specific characteristics, like high porosity and low density are caused by hardened cement paste in crushed concrete and the content of mortar and plaster in brick debris. Impurities like wood or gypsum and also harmful substances like organic pollutants may be a major problem for a reuse and should be minimized. Therefore unwanted materials and impairing substances have to be separated from the secondary building material stream. This can be done during the demolition process by using techniques for selective dismantling or during the subsequent treatment of the resulting rubble. Since almost all processing steps are associated with environmental impacts, the benefits of saving natural resources by applying secondary building materials should be weighed carefully. An environmental performance evaluation was undertaken to assess different techniques for reducing gypsum in recycled concrete aggregates, aiming at a minimization of elutable sulfates. These results were compared to the environmental impacts of the extraction of natural aggregates for concrete.