Circular construction materials

Interview with Dr. Anna-Vera Deinhammer, coordinator for the Construction Industry, and program lead for DoTank Circular City Wien 2020-2030 - December 2020

It was the beginning of 2019 when Vienna got together with 12 other European cities as part of the Big Buyers Initiative working group on Circular Construction with one mission in mind: improving circularity in the construction sector by promoting procurement of reused, recycled or reusable construction materials and dismantling works.

“This collaboration was the wind under our wings,” says Dr. Anna-Vera Deinhammer, coordinator for the Construction Industry, and program lead for DoTank Circular City Wien 2020-2030, “we strengthened the position of the topic locally and elevated it on a higher strategic level, and we learned from other cities’ experiences making our learning curve faster and better.”

Through exchanges with the cities in the group, Vienna decided to launch a first pilot project aiming to use recycled concrete and insulation material in new buildings to prove how the city could influence the market towards more circular solutions in the construction sector.

The City of Vienna started its journey towards circularity in the Seestadt Aspern, an urban expansion project within the city’s boundaries, just 15 minutes by subway from the city centre. Thanks to coordination and aligned ambitions in the early planning phases of the development, one million tonnes of excavated earth and aggregates sourced, cleaned and crushed on the site were used in the construction of 3,000 new housing units. Mobile machines ensured that 90% of CO₂ emissions were saved compared to using an aggregate processing plant 25 km away.

But this landmass coordination is only one aspect of a circular city. Another is planning and constructing buildings with a higher circularity factor. As Vienna plans the construction of a new building in 2020, this is the perfect occasion to showcase the use of recycled concrete and insulation materials. “They needed new buildings and we used the opportunity to suggest implementing recycled concrete and recycled isolation materials,” says Dr. Deinhammer.

How can a municipality influence the market, so it gets what it wants? As the offer of secondary material is limited at the moment, it is important that the city acts as a promoter of innovative solutions through the way it launches its calls and setting a precedent through its own public project. In the spring of 2020, Vienna started developing a tender for the new construction project that includes a list of criteria describing the perfect product.

“For example, we are discussing a minimum amount of gravel made of reused concrete,” explains Dr. Deinhammer “We thinking about indicating a minimum amount or proportion of secondary material use for each component, describing a reference product that represents the ideal offer, the dream.” Aware that they might not get a perfect match, this choice wanted to inspire the market to aim high, as the offer that came closest to the ideal would be selected.

As an additional step, the city will organise citizens’ outreach via a reused container pop-up office where information and photos from the pilots will be used to explain to citizens how the refurbishment will work and look using secondary materials, and the advantages of this approach. The city especially wants to address the scepticism that some citizens have around the quality of secondary materials. “We have to show and prove that using secondary materials in new buildings or in refurbished ones doesn’t affect the quality of the building,” explains Dr. Deinhammer.

The experience and the results of pilot projects such as these, as well as the exchanges with other European cities within the Big Buyers Initiative, have fed into Vienna’s wider DoTank Circular City Wien 2020-2030 strategy.

The strategy is based on three principles: reduce, reuse, recycle. The first refers to designing buildings with minimising use of materials in mind. Today, construction materials account for half of raw materials used in Europe. Therefore, lowering the consumption of raw materials means protecting our natural resources, reducing land consumption, preserving biodiversity, and acting responsibly within planetary boundaries.

 “It is important to emphasise that recycling is good, but we also have to start reusing the materials and the products as they are,” says Dr. Deinhammer.

Secondary raw materials can play a big role in designing our habitat to be more resilient and to be prepared for future climatic events caused by climate change, such as heavy rainfall or heatwaves.

A construction sector based on circularity means integrating the entire resource cycle of buildings from production to disposal or recycling into a sustainability concept, while avoiding waste and inefficient use of energy. However, the sector is currently not making the necessary connection between programming, planning, and execution to achieve this goal.

“We are not changing the way we build; we need to change the way we approach a construction project,” says Dr. Deinhammer. For example, every construction activity begins with the supply of raw materials, which are further processed and assembled into components, so the decision to prefer a certain construction method will also decide the whole material’s lifecycle.

As the sector involves many actors, such as developers, planners, users and building owners, for a successful approach to circular construction they all need to be involved and play a role in applying the principles of circular economy. “Our key learning is that we need to do this together,” says Dr. Deinhammer “with so many actors all across the value chain, we need to combine municipality with research and, of course, with the market.”