- Seen and unseen
- Fabric formwork
- Formwork construction
- Freedom within the mould
- Learning by doing
Sheets of woven textiles can be used as flexible, lightweight formwork for concrete structures. The relevance of developing fabric formwork touches upon two fields of evolution: that of concrete construction, which has continued for millennia, and that of textiles, with an even longer history – recently of an almost revolutionary character.
Concrete is the most widely used building material worldwide. At the same time developments in digital design and engineering tools have changed the way architecture is conceived and calculated. However, methods for constructing concrete structures haven’t developed at the same pace; the architectural vocabulary of concrete can be developed with regards to form, structure and surface in order to exploit the potentials of the so-called liquid stone.
Textile technologies have undergone an immense technical development, in which existing, previously crafts-based production techniques are combined with new or alternative material fibers and scales in order to produce flexible, strong and light fabrics with new material properties. As such, textiles are finding their way into construction at different scales. With regards to formwork it could be asserted that the carefully considered combination of textile technologies used as formwork for concrete may participate in unfolding potentials for concrete and extend its existing architectural vocabulary.
There are two technical characteristics about fabrics which are essential when used as concrete formwork. The first technical aspect is that fabrics act in tension under the hydrostatic pressure of wet concrete. This dynamics results in a bulging surface between points of restraint. The deflections are all catenary curves, which indicate that the forces are spread evenly all along the fabric surface. This means that fabric is an effective formwork material in transferring the pressure upon the inside to the entire surface That’s why so little fabric can hold heavy amounts of concrete. The second technical aspect deals with the porosity of woven fabrics. Excess air and water go through the formwork membrane as the concrete is poured – the fabric appears to be sweating – it results in fewer blowholes and a higher level of cement compared to water – the so-called water-cement ratio is low. A smooth, tight concrete surface is desirable because it is stronger and less likely to crack.
A third, formal aspect is the result of the two technical characteristics. The direct formal consequence at stake in fabric forming seems to be the most architecturally intriguing.
Concrete will always show the imprint of the surface structure and connections of the applied formwork material, yet this is particularly expressed using fabrics: the form, size and placement of restraining device, and the detailed weave of the chosen fabric will show on the form and surface of concrete. This reveals the narrative of architecture becoming embedded in concrete.
With kind assistance of Greek author Iosif Alygizakis I’ve attempted to coin a word attempting to embrace this duality in, on one side, the experienced, sensed qualities of a cured concrete structure as material and, on the other, those almost metaphysical traces of becoming that may be the most poetic feature of concrete! Stereogenés is Greek. It consists of two words, stereo, solid, and genés, derived from ginomai, procedure of becoming. Cured concrete then is stereogeneous, solid but, as the word indicates, obviously has become so through a number of processes from a liquid state. These procedures to become happen through chemistry and statics; the chemical processes within the concrete mix when cement reacts to water; and the formwork statics when the form is filled with concrete. Both are results of human actions: the former through the design of the concrete mix; the latter through the design and construction of the formwork tectonics.
Concrete construction can be seen as a series of carefully conceived and executed processes that inform concrete architecture. One can look at the potentials for the future implementation of fabric formwork in several of them, namely in the design and production of fabrics; of ‘haute couture’ or mass-produced fabric forms or concrete elements. Concrete is nothing without its process – yet is definitely something during its use, and something more than merely a space-defining structure. The further unfolding of Stereogeneity will attempt to create a holistic view of concrete as both process and material.
by Anne-Mette Manelius
Royal Danish Academy of Fine Arts, School of Architecture, Copenhagen