- Seen and unseen
- Fabric formwork
- Formwork construction
- Freedom within the mould
- Learning by doing
Concrete is a universal building material, which can take many forms – ‘the material of metamorphoses’ – as written by Ola Wedebrunn (Betong, 1996): ‘Concrete is the material of change, of metamorphosis. Like a chameleon it appears in different disguises and in different contexts. The assessments of this substance have changed over the years. In the early modern period, it was considered to be a miracle material, which would solve all the problems of the building industry. Later it was seen as representing the inhuman scale of large building projects and sharply criticized. In many ways concrete is a universal material. It can take any form and shape, and it is made up of raw materials, which are so commonly found that they can be extracted and produced virtually anywhere. Still, concrete represents particular values that are hard to define but, at the same time, seem to be associated with modernity in architecture by many.’ … ‘Concrete is predominant in our culture. Hence it is important that we appreciate this material and that we learn to understand and assess both the technology and the means of expression that go with it.’
The term ‘Concretum’ refers to the ‘forgotten’ Roman method of building, using the volcanic earth material ‘pozzolan’ as a hardening mortar, tying stone and bricks together. Roman pozzolan concretum was used unreinforced for walls, vaults and dome constructions. In many ways it was a coherent building method, superior to stacked walls and arches of brick and lime in terms of formability, strength and span. The still standing aqueducts and the grand dome of Pantheon in Rome, built around year 120, give evidence of this material’s potential and the art of engineering mastered by the Romans. A technology which was forgotten with the fall of the Roman Empire and was unrivalled until the nineteenth century. Concrete is reinvented in the first half of the 19th century, re-establishing the properties of volcanic ashes by burning earth material, lime and clay to cement. It was given the name Portland cement after the concrete’s similarity to Portland stone. Concrete’s ability to harden under water was first used for building lighthouses along the English coast. After reinforced concrete was invented in France, this new construction material emerged and was used for building infrastructure, bridges and industrial buildings. It took much longer before it became an attractive material in architecture as a serious alternative to traditional building materials.
One of the pioneers, Auguste Perret (1874–1954), invented buildings with concrete constructions. In the beginning the visible concrete surface was decorated by glazed ceramic elements (rue Franklin, 1905). Later he refined the surface of the concrete by elaborating the handling of the concrete mixture, form details, profiles and surfaces. In rebuilding Le Havre after a totally new city plan (1946–1965) he used concrete as a universal building material for all buildings, domestic buildings as well as churches. ‘My concrete is more beautiful than the stone: I work at it, I chisel it. Concrete is a stone which comes into existence.’ (Auguste Perret, Église St-Joseph1951–1959)
Le Corbusier introduced reinforced concrete as modernism’s new material, and with his building and writings he provided the theoretical foundation for a new architecture of columns, open plans and facades. At first with a characteristic use of white cubist surfaces (Villa Savoye), later with untreated cast-on-site structures marked by the form’s material, texture and imprint on the raw concrete (Unité d’Habitation, Nantes 1953–1955). Concrete’s actual breakthrough as a general building material in Denmark only happens when the house building takes off again after World War II. The aim is to rationalize the traditional building process of brick and wood, transferring the execution from the construction site to the factory with the use of prefab concrete elements. Theoretically and technologically Denmark pioneers with its prefab construction until the economy stagnates during the 1970s. This is the background for the extensive use of concrete elements in the Danish building industry. Concrete and concrete elements are used in many different ways, with more or less clarity and tectonic significance. Concrete may serve exclusively as load-bearing construction with no visible effect on the form or texture of the building. Or the presence of concrete may be perceived as crucial to the building’s idiom and surface texture.
Lastly, concrete elements and surfaces may be an integral part of the building’s architectural statement. Via his architecture Jørn Utzon (1918–2008) has made an impact with his deliberate tectonic use of cast-on-site concrete in combination with juxtaposed prefab elements. The ‘plinth’ of the Opera House in Sydney is supported by beams which are shaped and cast on site, whereas the large ‘sails’ are made from joined, stereometrically modulated elements. His church in Bagsværd is built with a similar combination of the two techniques – elements in the shape of frames and fillings form the galleries and support the transverse, cloudlike vaults, which are cast on site as thin, reinforced shells with visible imprints from the formwork.
Lundgaard & Tranberg Architects have used concrete innovatively in their buildings, both in terms of structure, space, texture and process. The recently completed SEB Bank Headquarters (2011) consists of nine towering silos, which constitute the core and support the thin, organic decks of the two buildings. The towers are cast on site in sliding formwork in an uninterrupted casting process. The concrete is carefully treated as part of the interior surfaces, which vary from grey cast concrete over white poured cement to polished concrete, revealing the granite stones. Space and surfaces continue out in the terraced landscape park. BIG, Bjarke Ingels Group’s, projects in Copenhagen’s Ørestad district represent a creative but more pragmatic attitude to building in concrete. The VM project’s structural principle is based on standard load-bearing concrete walls and non-bearing lightweight facades. The V-building has an inside common corridor space that gives access to apartments with one, two or three storeys and many different spatial variables.
The three mentioned architects’ projects illustrate different attitudes to the use of concrete in architecture. For BIG’s office, the use of standard elements in concrete is a pragmatic way of minimizing costs, a tool to be used for a new conceptual play with variety in space, colour and surface. The concrete in itself is neither visualised in form, elements or surface. L&T Architects think and visualize both the process of building, materiality and details in a straightforward way by using concrete both for structure and surfaces in a simple, but sophisticated play with selected contrasting materials; whereas Utzon’s buildings reveal a specific tectonic approach. His architecture both forms and expresses the buildings’ structural and complementing elements, and the additive forming principle is supported by the clear expression of surface materialities and the serenity of details.
by Peter Sørense, Associate Professor, Architect MAA
Royal Danish Academy of Fine Arts, School of Architecture, Copenhagen