Nathalie Reiz

Concreted Zurich - A Distortion of Correspondences

A large blue crane is hovering proudly over the calm lake water. Graffities in all colours and languages are sprayed on it, like an urban projection screen. Our habitat is talking to us and so are we. Many of the sprayers won’t know, that this crane has lifted in the last one hundred years the foundation material of the city of Zurich. Millions and millions of tons of sand and gravel have been unloaded here every day coming from the Upper Lake of Zurich with the so called “Ledischiff”. The days of the “Ledischiff” are over by now. The city is built. Or is it?

Case Study Kibag Concrete Plant Zurich Wollishofen

Behind the obsolete looking crane, there is still the Kibag site in Wollishofen producing 120’000m3 of concrete for Zurich every year, enough for 800 new single family houses. In my research I observe this concrete plant closely. From the interior the calmness of the lake vanishes and blurs into a dull humming. Sand and gravel rattle over the conveyor belts, the fine dust of cement is blown through pipes, addititves wait in their tanks to be used and water is rushing into the concrete mixer. The end result is an elegant flowing shapeless grey mass, which will make its way to build the city of Zurich, my habitat. But where does this material come from and how does it correspond to our built environment in the city?

Resource Flows of Concrete: Impacts on Soil & Atmosphere
To investigate this, I look into the resource flows of concrete of the Kibag site. This research takes me to carved-out landscapes, which are blasted open, washed away, dredged out, removed and refilled in an almost brutal act of man-made transformation. The terraced Gabenchopf quarry, which mines limestone and marl for cement production and the gravel pit in Stadel show me how much material humans move every day to further expand their habitat. However, it is not only the soil that is transformed; at the cement plant in Siggenthal it becomes clear how much particulate matter and exhaust gases, the most prominent of which is CO2, are released into our atmosphere almost without limit. Hundreds of lorries roaring from the extraction sites to the plants, to the cities and back again every day exacerbate this problem by their exhaust fumes and traffic nuisance they create.

Distortions of our Habitat

Not only is the impact of concrete on our natural habitat evident, but also where the material is used, on our construction sites and our cities. In the course of the 20th century due to the invention of reinforced concrete as probably the most efficient and scalable building material of modern times, huge infrastructures, roads, railroads, residential and commercial buildings are built. In our city, holes are dug, piles of earth are transported away and covered with concrete. As much as we seem to need concrete for our livelihood, it is also the antithesis of everything natural that we know in our habitat. It is the building material that reveals the distorted correspondence between the artificial and natural habitat.

Actors: Conflicts and Negotiations around Concrete Processing

Where such distortions occur, there are various conflicts and negotiations that arise in the processing of this highly conflictual material. To investigate these conflicts and negotiations further, I talk to various actors such as representatives of the planning and construction industry, the responsible authorities, residents, professional associations, but also researchers. Sometimes the actors are not human, like different animal and plant species. I then read about their habitat and how they inhabit these spaces. Sometimes the actors are also not traceable to a single person to be interviewed, but rather found on the site itself, like graffiti or posters or even in a virtual form like comments on the internet.

Possible Approaches to the Current Resource Flow

Nevertheless, it is impossible to imagine our habitat without concrete as a building material. We still pour around 2m3 of concrete per person per year over Switzerland. This mass of concrete alone, together with the large-scale infrastructure and the local availability of its resources, makes it almost impossible to replace all of it with alternative materials such as wood. In addition, there are also infrastructural buildings or certain public buildings for which concrete is difficult to substitute thanks to its formability, water resistance and durability. Therefore, we must find a solution how to deal with the building material in the fu- ture in order to ensure a sustainable and responsible use for all actors and habitats. This is why, in a final research step, I look at the current state of research for more sustainable processing of concrete and try to locate where these approaches act in the whole flow of resources. From approaches like reduction of CO2 emissions, to circular economy strategies, over to the change of planning standards.

Design Approach: Kibag Site as Recycling and Testing Hub

But where can I act here as a designer? By re-developing the Kibag site into a testing ground for a new concrete economy, where all material flows, challenges and conflicts come togeth- er, I act on the entire resource flow. In my design proposal, I provide a new recycling center for the city of Zurich, by reactivating the lake for a transportation system of demolition material. Moreover the area becomes a testing ground for various new technical possibilities of concrete to investigate which architectural form language and type of construction can be applied to it. The Kibag concrete plant remains open too. It promotes the scalability of these concrete processes and brings these tested concrete variants directly to the city. The testing ground, which is located next to very public spaces in the city, should also be opened to the public towards the lake and become a place of exchange for citizens, builders, architects, industry represen- tatives, authorities or any other affected actor. Because every innovation of the material brings new conflicts and negotiations, which need to be elaborated further. With that the Kibag site becomes a space to negotiate and demonstrate the potentials of concreting, showing how this material can again correspond to the habitats it produces.

A Manifesto for New Concrete Correspondences 

– 10 Strategies for the Kibag Areal in Zurich-Wollishofen

I. Let’s keep production within the city of Zurich!

Production should be as close as possible to the city of Zurich, to keep jobs and reduce transportation. This principle is all the more important for concrete as a building material. The Kibag Areal offers a great potential to remain a productive site in the city of Zurich. The site, where concrete has been produced for almost 100 years, is ideal due to its good location being near to the city centre and guaranteeing possible transport connections through the lake and the railway. Local material transport and fast connections to the neighbouring construction sites will be efficient and resource-saving. Production for an industry that urgently needs to take a step towards sustainability needs space in the city to present and to discuss in order to drive possible solutions forward.

II. Let’s treat Zurich as a resource through activating the lake!

The Kibag site in Zurich Wollishofen will become a new recycling centre for the reuse of demolition and excavation material. To this end, the obsolete crane, which was originally used for loading gravel, will be reactivated so that the lake can once again be used for transportation of goods. This should not only bring the centuries-old tradition of material transport on the lake back to Zurich, but also will activate different locations along the lake. The densely populated area around the lake will become an urban mine for the future production of concrete. Loading stations can be built or reused at Kibag’s existing harbours. In addition, this network can also be made denser by adding further loading stations at the landing stages of the Zurich shipping company. In this way, a largely recreational lakescape can be transformed back into a productive one. “Ledischiffe” sail alongside sailing and rowing boats. Tonnes of materials are cruising over the calm lake water, ready to return to the cycle or materials.

III. Let’s strengthen existing infrastructures with new innovations!

The existing infrastructure of the Kibag site for concrete remains in place with all its buildings, some of which date back to the late 19th century. However, the over time functionally grown processing infrastructure needs to be extended to deal with the new material flows that will enter the site. In addition to the reactivated crane on the lake for transporting materials, a new connection to the rail network is also to be created, with the materials being lifted by crane over the main road. This will create an interweaving between the existing and new infrastructure, which will give the site a new expression and liveliness.

IV. A new recycling hub for a circular economy!

New recycling plant and silos are built between the existing production line and the Rote Fabrik to process the new material flows. Firstly, the washing and sorting plant for contaminated materials, then the industrial hall for the crusher and finally the silo for those materials that are not processed into concrete but are transported directly by rail or lorry to construction sites or other plants.

V. The Kibag Areal as research and testing ground!

In order to be able to build sustainably with concrete in the long term, it is not only important to promote the circular economy, but also to be able to drastically reduce the high CO2 emissions when building with concrete. To this end, a new research centre and testing ground is established on the Kibag site. The building materials laboratories and test workshops are located in the existing buildings of the former Kiefer window factory, with new testing units to be built on the roof of the building. On the one hand, they emphasise the importance of the new material in terms of urban planning and, on the other, the testing units will be visible from the busy street.

VI. Make concrete architecture sustainable again with productive case studies!

All new built structures for the centre for recycling and research are case studies, which are trying to test different design solutions and architectural expressions for a more sustainable use of concrete.

a. Washing Plant: The newly created washing plant consists of an unreinforced solid tamped concrete structure with the lowest possible cement content and a high proportion of recycled excavated and demolition material. The very solid walls are designed to withstand the vibrations, while the tensile load is borne by an internal steel skeleton.

b. Recycling hall: The recycling hall for the concrete crusher and CO2 gassing requires the largest possible spans for the machines. A thin shell construction with optimised static form-finding and reusable formwork is therefore used. The aim here is to achieve the largest possible roofing with the smallest possible use of materials.

c. Silo: The new horizontal silo, which consists of barrel vaults, adopts the original pressurised construction method from Roman times, with each barrel vaults consisting of different recycled materials and clinker proportions to test different mixtures under weathering and load.

d. Primary structure for testing units: The basic structure for the extension on top of the building is to be constructed from bolted prefabricated concrete elements, which can later be dismantled and reused without having to demolish how elements.

VII. Make the production public!

The front part of the site facing the lake provides a new green space for the neighbouring quarter. The Wollishofen community centre meadow will be enlarged and the quarters’ building itself will now stand as a pavilion in the newly created park. Visual references to the productive area open up with a new view of the silos and the mountains of material to be stored, which should give the public an insight into the materiality of their built city. The uncontaminated, reprocessed materials bordering the park will thus become part of a landscape park.

VIII. Create permeability on the productive site!

The existing public lakeside path is extended and supplemented to introduce new permeability to the area. On the one hand, a new connection to the lake is created and, on the other, the two culturally important neighbours for the district, the GZ-Wollishofen and the Rote Fabrik, are newly connected to the site. For that new paths and ramp connections are created. One ramp connects the Rote Fabrik to the site. Here, the path leads between the new recycling plant and the new silo, providing insights into the processing of materials. The ramp also crosses the material conveyor belts and lorry traffic. Another new silo will be surrounded by a public ramp leading to a raised walkway around the silos. This vertical park, which is also planted with greenery, will become a recreation area and lead to a viewing point and diving platform directly on the water next to the existing crane system. This creates views of the lake and the newly created park.

IX. A space for human and non-human actors!

The area should not only be accessible to people, but also create a habitat for plants and animals by the lake. The new case study buildings offer space for breeding grounds and new plants along the façade. The piles of material that border the park will become a habitat for pioneers thanks to their open space.

X. A space for negotiations!

As a new public production and research centre, the Kibag site is intended to promote sustainable future construction with concrete. It should be a place where various stakeholders can come together to find and discuss future sustainable solutions. Stakeholders from research, production, authorities, planers, and the general public will be able to reflect on the building material and its future use.