Zurich and the art of concrete recycling

Is it possible to build houses with recycled con­crete and what impact does this have on costs, environment, safety and aesthetics? Concrete is essential in modern construction. It is a highly flexible, resistant and stable material. But there are downsides: gravel, one of the main compo­nents of concrete, is a finite resource; cement is energy-intensive in production, and mining and transport degrade the environment.

At the same time, construction and demoli­tion (C&D) waste is one of the largest waste streams in the EU. According to the European Commission, 25-30% of all waste generated in the EU consists of C&D materials such as concrete, bricks, gypsum, wood, glass, metals and others – many of which can be recycled.

Instead of landfilling, cities today are looking at ways to use these resources more efficiently and in an environmentally friendly way. In the sense of ‘urban mining’, one option is to recycle the mineral components of C&D waste to make new concrete. This allows the construction sec­tor to preserve natural resources, avoid landfill and protect precious landscapes and habitats.

Reusing old materials in new buildings increases their resource efficiency and makes the construction sector less dependent on scarce resources such as sand and gravel. It can also improve the energy balance of new build­ings, especially if materials are recycled and reused locally. It is a step towards closed loop resource use. But many cities are not aware of the opportunities that recycling construction materials bears.

The Zurich art museum, the Kunsthaus, is currently undergoing a major extension. Designed by architect David Chipperfield, the new complex is made almost entirely of con­crete with recycled aggregates and CEM III/B cement (where conventional clinker is replaced by slag sand), including the indoor space shaped by widely exposed concrete.

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published on www.mrw.co.uk

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