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Tectonics in Building Culture

Concretum (2010)

The modern construction industry has established methods to build concrete elements with great efficiency and precision through the development of innovative formwork technology. Often the realisation of concrete form is greatly influenced by the formwork construction, and sometimes it is even seen as design restraints. In any concrete project the initially conceived design should take account of the available formwork solution to minimize any design modification at later project phases due to the initial design’s impracticality. Thus continuous research and development of formwork technology can free more imaginative concrete forms, and the exploration of the use of fabric formwork for concrete construction has its purpose to find more innovative ways to express the material’s aesthetic quality while increasing the construction’s practicality.

Concrete in its initial state is liquid, and not only can it be moulded into various forms but it can also copy the texture of what it is cast against. To express this material quality of concrete conventional rigid formwork has its limitation. On the other hand, flexible fabric formwork can mould concrete into more organic and self-defined forms with a minimum of cost, time and labour compared to formworks made of timber or steel. It is true that fabric formwork requires other supporting elements made of rigid materials to hold the fabric in the right positions, however, as there are more supporting elements, the amount of construction work increases. Therefore, ideally, this should be kept to the minimum.

The fun of using fabric as formwork lies also in choosing the right types. The decision should be made based on a number of factors including the fabric’s ability to sustain the weight of poured concrete, colour and texture of fabric (as they will be imprinted onto the concrete), pore sizes (this governs the mechanical properties of concrete such as the durability and strength; for example, with the pore sizes being too large, the cement particles will escape with the excess water in the mix and in fact reduce the quality of concrete. Thus it is important to choose a fabric with the right permeability (in order to filter out only the excess water) and stiffness.

Stiffness is an important characteristic of fabric to consider in the formwork construction. Often the use of stiff fabric causes excessive creases and folds, which may later be trapped between cast concrete, and these become impossible to remove. However, if the fabric is too flexible, it will deform too much under the weight of the concrete, and the geometry of the cast form would be different from what was initially intended. In such cases the fabric could be further tensioned to overcome the excessive deformation. Fabric formwork has both aesthetical (organic, flexibility, texture and colour) and practical (light, affordable, compact and durable) merits, and there are an increasing number of global interests. Yet for its future growth it is considered that more commercially driven developments are required at this time, and it is important to develop the fabric formwork technology to the level where it can completely duplicate the conventional concrete structures cast with the rigid moulds. With extensive research and development it has the potential to be used as commonly as steel, timber and other formwork materials.

Daniel Sang-Hong Lee
Royal Danish Academy of Fine Arts, School of Architecture, Copenhagen