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What does it take to reuse a concrete element?

September, 3, 2018

There is a wind of change in the building industry at present. Everybody preaches sustainability and overall economy. And there are several good reasons to do so - no doubt about it. An overall economy mindset and a new sustainability code as an addition to the existing building codes and are important to the developer. Many people forget, however, that overall economic efficiency does not end at operation and maintenance of the building, but also concerns demolition and reuse of the materials the building is made of, either as sub-components in other building elements or in their actual design – as complete concrete elements. In popular terms this is called circular economy.

Concrete as the building material of the future

Even though it is impossible to make predictions about the future, most people probably agree that, due to the many unique properties of concrete, also in the future concrete will be the main building material from which load-bearing structures are made of. Therefore, it is of crucial importance that the concrete industry has a sustainable and circular mindset in all its phases - from developer to architect, engineer, contractor and supplier, and in demolition, reuse and not least reconstruction phases. Since the first project stages at the developer’s and the architect’s, the ambitions concerning sustainability (in combination with known and well-documented solutions) must be incorporated–– including concrete structures.

 

Bolted connections – Design for disassembly

But what does it take and how big changes are required to be able to reuse a concrete element; for example, a wall element, in its original design? It is a common impression that enormous changes are required to transform the building industry to be more sustainable, circular and environmentally-conscious. But with small, relatively simple adaptations it will be possible in the future to reuse separate building elements from a complete element building, and thereby preserve the high value of concrete elements.

For static reasons, it is necessary to interconnect the concrete elements. For many years, this has been solved by designing and making assembly details where the elements are cast together, typically by means of corrugated tubes with continuity reinforcement built in. But with such a design, it isn’t possible to separate the elements without destroying them. If, on the other hand, you incorporate connection details where the elements are bolted together, there is also a possibility of disassembling the elements and thereby reusing them. This connection detail is a known principle for load-bearing steel structures. But incorporating this in concrete structures is a new idea to many.


Legislation as an incentive

Many investors and developers brand themselves as environmentally-conscious by certifying their buildings by means of schemes such as DGNB, LEED or BREEAM. The end users of the buildings also pay attention to these certification schemes; indeed, it does make sense to have them. The problem is, however, that at present these schemes are voluntary. With legislation in the area, both public and private owners would be forced to consider sustainability. In addition to this, it is decisive that in the certification schemes the weighting of the design concept, demolition and reuse should be sufficiently high for motivating the owners and architects to incorporate design for disassembly – already in the development phase of the project.

 

Extensive experience combined with a new focus and new knowledge creates new solutions

The industry needs visionary pioneers. The construction industry already has enterprises with focus on sustainability and where the entire business concept is based on these principles. A good example is a Danish architecture company GXN. But we still need far more enterprises that place sustainability at the top of the agenda; enterprises that think innovatively and benefit from their experience and competences from the building industry. There is a need to develop and rethink the way in which design and construction are carried out so that after their lifecycle is over, buildings can re-emerge with the original static properties maintained.

At Peikko, we have a clear, long-term strategy to contribute with solutions for a sustainable circular economical mindset in which the reuse of concrete elements takes part. Read more in this White Paper: In search of a bright, circular future!

 

Case - Circle House

A good example of a project in which the circular economy mindset has been incorporated is the Circle House project at Lisbjerg, Aarhus, Denmark. It is a social housing project where the goal is to have not less than 90% of the building materials suitable to reuse without losing any noticeable value. The project is estimated to be completed in 2020. This project will be a demonstrator showing that with known construction principles, such as the use of concrete elements, you can achieve a circular economy result. By using carefully prepared design principles and details, such as bolted connections, you can design a complete building with concrete elements – with the possibility of disassembling and reuse. This strategy is a good choice for developers with a long-term goal. Read more about the project here: https://www.lejerbo.dk/om-lejerbo/byggeri/circle-house

A demonstrator of the Circle House project has been built and can be visited at the following address: Gl. Køge Landevej 26, DK-2500 Valby. You can watch a video of the project here.

Jonas Høg
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