[2-meter high fabric-formed concrete column]
The use of flexible molds entails a direct formal relation between the tectonic principles of the formwork structure, the type of concrete pour, and its concrete consequence, so to speak. It is a potential to develop the details in formwork construction because they are technical as well as aesthetic/form giving. On the other hand, this formal consequence means that all mistakes show themselves as well with equal power, and this is a disadvantage of the building method unless you see mess-ups as a charm. The dilemma of course is that working meticulously in construction shows high-level craftsmanship. This comes at a price in hours and wages, in Denmark 70% of the cost of concrete elements go to wages.
[Images of fabric-formed plaster model 1:4]
One of the student groups at the 2013 TEK1 workshop at RDAFA also concluded this from their preliminary experiments with fabric formed plaster casts. When attempting to literately tailor the fabric formwork the ruthless character of the poured plaster changed initial intentions to less controlled and little desired folds and bulges (not shown here). It took a long time to work with intricate principles and it still proved difficult to anticipate and achieve the results they desired. As a result, the students devised a formwork principle that, while simple to construct, would still result in sharp, controlled edges as well as soft curving surfaces. The principle was tested in the model shown above
Formgiver and structure
The storyboard shows the steps of constructing the column and the simplicity and tectonics of the structural formwork principle. The title is Compression and Expansion and refers to the role of the formwork sheets and the consequence on the poured fabric mold. I love how the interlocking and formgiving mdf-sheets are also what holds up the fabric tube. The principle means that the column has a square footprint and always two flat surfaces and two curved ones, i.e. quite a complex geometry.
[Left: the formwork structure ready for the pour. Right, detail of the formwork structure before stripping ; bits of cement has filtered through the fabric along with excess mix water during the pour.]
[Sketches from student report showing the principles and the steps of constructing the formwork]
Creases and shifts
Despite their work at simplifying the process for ultimate control, for the resulting fabric-formed concrete column, students were unhappy about little creases from the fabric as well as the asymmetry of the bulges. Especially the bottom has uneven bulges, which could have been avoided by adjusting the fabric tube before and during the pour, as well as working the concrete from outside the formwork – simply moving the fresh concrete by pushing against the membrane mold. Note, however, how identical creases can be found on the surface of the plaster model cast using the same principle.
This first meeting with concrete and principles formwork tectonics for first-year students is promising. If you are in Copenhagen, swing by the quay behind the RDAFA and check out the columns.
Work and drawings by: Oskar Mannov, Sidsel Petersen, Nora Ødegård, Cuong Tran, and Toke Ridderson.
TEK1 2013 concrete workshop organized and taught by Finn Bach, Tenna Beck, and Anne-Mette Manelius (yours Concretely) for the Institute of Architectural Technology at the RDAFASA