Vacuumatics 3D-Formwork Systems: Customised Concrete

The Masterbuilder - June 200978

Vacuumatics 3D-Formwork Systems:Customised ConcreteArchitecture

Vacuumatics 3D-Formwork Systems:Customised ConcreteArchitecture

The latest developments in concrete technology,like Ultra High Performance Concrete(UHPC), Fibre Reinforced Concrete (FRC) and

Self-Compacting Concrete (SCC), enlarge the poten-tial of concrete as a structural material. As a solidifiedliquid concrete has the unique material quality toreveal the specific characteristics of its formworksystem. The limiting factor at the moment withrespect to the feasibility of concrete in the free-formdesign practice is the manufacturability and adaptabil-ity of its formwork system.

This paper describes an adaptable mouldingtechnique to create complex 3-dimensional geom-etries in concrete, citing ongoing research onVacuumatics 3D-Formwork Systems at theEindhoven University of Technology (figure 1).Vacuumatically prestressed structures, vacuumatics inshort, rely on the structure principle of prestressingincoherent (structural) elements inside an enclosedskin by introducing a (partial) vacuum inside thisenclosure. The abilities of vacuumatics to be repeat-edly "free-formed" and to create customised surfacetextures provide the ideal boundary conditions for atruly flexible and adaptable moulding technique tocreate geometrically complex shapes in concrete.

Our modern society can be characterised as rapidlychanging and merged with individualisation andcustomisation. Furthermore, buzzwords like "adapt-able", "responsive", "dynamic" and even "smart" and"intelligent" are more and more common in modernbuilding design. A truly flexible and personalisedliving environment with changing identities seems tobe inevitable. In contemporary building design itcannot be ignored that so-called "blobs" (from: binarylarge object) are very current phenomena. Thisparticular trend finds its origin in vast developmentsof advanced digital design systems and CAD/CAMprocesses. In reality, these "free-form" designs ofbuildings and structures are realised by applying apre-formed (decorative) skin onto a regular primaryor secondary, mostly rectilinear, load-bearing struc-ture. The main reason for this building method can befound in the fact that the current building industry ismainly rectilinearly oriented, and thus not capable ofanticipating to the 3-dimensional free-form tendencyin architectural design. A different approach to designas well as manufacturing is required in modernbuilding design.

Concrete Architecture

From a material point of view it would seemevident to use curable liquid-like materials to createthe desired irregular and fluent shapes. Concrete forinstance is a strong material in solidified state yetfluid in origin. It has therefore practically unlimitedform possibilities. The latest developments in con-crete technology, like Ultra High PerformanceConcrete (UHPC), Fibre Reinforced Concrete (FRC)and Self-Compacting Concrete (SCC), enlarge thepotential of concrete as a structural material (figure 2).

F. HuijbenPhD Researcher / Structural EngineerEindhoven University of Technology (TU/e)Department of Architecture,Building and Planning Eindhoven, the Netherlands

Figure 1: Research on Vacuumatics 3D-Formwork Systems

Research: 3D Formwork Systems


Figure 2: UHPC - "Folly Zonnestraal"

The limiting factor at the moment, with respectto the acceptance of concrete in the free-form designpractice, is the manufacturability with in particularthe adaptability of its formwork system. Any changein shape or surface texture can be regarded as com-plex, time-consuming, labour-intensive and thusfinancially unattractive. What is needed is a flexibleand adaptable formwork system to realise the re-quested geometrically complex shapes and surfacetextures in concrete (figure 3). This would encouragethe statement that the choice of building materialshould be based on the best performing structuralsystem that meets the user's needs, rather than on thedifficulty of design or construction.

Vacuumatics

Vacuumatically prestressed structures,"vacuumatics" [1] in short, rely on the structuralprinciple of prestressing incoherent (structural)elements [2]. This is established by introducing a(partial) vacuum inside an enclosed flexible skin withunbound filler elements. The atmospheric pressureacting on the covering skin causes this skin to betightly wrapped around the surface of the filler

Figure 3: Formwork Efficiency

elements, hence "freezing" the configuration of thefiller elements in its current state [3]. This techniqueleads to rigid load-bearing structures. The differentialin air pressure prevents the filler elements from losingcontact in the tensile zone of the structure whenexternally loaded (figure 4). The principle of pre-stressing a material of low tensile and shear strengthto produce considerably enhanced properties intension is well known. The principle of vacuumatics isto some extend analogue to that of concrete pre-stressing although the pressure created withvacuumatics is multi-directional. As a unique featurethe original flexibility of the structure is fully restoredonce the vacuum pressure is removed.

Shaping Aspects

The main advantages of vacuumatics are theirform flexibility and adaptability enabling the produc-tion of a wide variety of 3-dimensional shapes fromone single structure. An important factor that deter-mines the adaptability is the so-called "flexibilitycontrol" (figure 5). Without any negative pressure(0% vacuum) the filler elements inside the flexibleenclosure possess hardly any consistency. Thereforethey are able to flow freely inside this skin, resultingin a fully flexible structure. By increasing the amountof vacuum pressure the consistency of the fillinggradually increases, resulting in a more or less plastic

Figure 4: Structural Pre-stressing Principle

FormworkEfficiency

Traditional (timber)

Engineered (metal)

with rubber sheet

Fabric-formwork

Sand moduling

CNC-milled moduling

"Ideal formwork"

Free-from design

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customization

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adaptability

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Accuracy

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demouldability

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Low initial costs

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Re-usability

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Manufacturability Quality Cost Efficiency

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Research: 3D Formwork SystemsVacuumatics 3D-Formwork Systems: Customised Concrete Architecture


behaviour of the structure. This enables the structureto be freely shaped while maintaining its newly givenform. Finally, in fully deflated state (near 100%vacuum) the vacuumatic structure becomes rigid,largely dependent on the exact properties of the skinand filling materials used. The reversibility of thisrigidifying process enables vacuumatics to be(re)shaped all over again.

In order to literally mould vacuumatics into"any" desired shape some sort of morphologicaltooling is required that forces the filler elementsinto their requested configuration. Especially theability to locally adjust the geometry has greatpotential with regard to the customisation ofstructures. The so called "form-fitting" capacity ofthe vacuumatic structure as the skin itself wraps thefiller elements in vacuumatic state contributes tothe vivid sensorial experience of the structurevacuumatics (figure 6).

Figure 5: Flexibility Control

Figure 6: External and Internal Formfitting

Materialisation Aspects

Although theoretically many types of fillermaterials can be applied with vacuumatics theirenhanced structural properties in deflated state areessential. The packing of the filler elements as wellas the specific material properties heavily influencethe structural properties of vacuumatics with respectto their strength, stiffness and stability (and there-

fore safety and usability). Granular shaped materialsfor instance are known to pack closely togetherunder compression (figure 7) resulting in a consider-able amount of structural rigidity. Fibre-like materi-als on the other hand tend to behave like a tightlyinterwoven structure under compression henceacting like a composite-like structure (figure 8).Self-evidently all sorts of combinations and configu-rations of filler elements can be created for all sortsof (architectural) purposes. The enclosing skin doesnot only ensure the structural integrity ofvacuumatics, as it provides the structure with itsessential air-tightness, its material properties alsoseem to heavily influence the geometrical andstructural potential of vacuumatics [4].

Figure 7: Balloon Structure

Figure 8: Straw Structure

Vacuumatics 3D-Formwork Systems

The abilities of vacuumatics to be repeatedly "free-formed" and to create customised surface texturesprovide the ideal boundary conditions for trulyflexible, re-usable and, most importantly, fullyadaptable moulding techniques. This enables us tocreate geometrically complex shapes in concrete. Ourresearch on vacuumatics 3d-formwork systems



focuses on three essentially different types offormwork systems.

As an addition to standard formwork (figure 9a),the vacuumatics part is added to a standard formworkstructure. After the curing of the concrete thevacuumatic structure can simply be re-inflated, orrather "re-flated", and peeled off while leaving behindits imprint in the concrete surface. In contrast toprofiled rubber sheets the surface texture of thevacuumatic structure can easily be adjusted by

Figure 9: Vacuumatics 3D-Formwork Systems a, b and c

repositioning the filler elements. If required, thefilling can even be replaced entirely to create acompletely new type of surface texture.

The infilled-frame formwork system (figure 9b)consists of an external load-bearing frame structurefilled in by a double-sided vacuumatic structure. Inbetween these two parts the concrete is poured.Since the edges of the formwork system remainfixed this facilitates easy connectivity of the castelements, whereas the two flexible inner parts ofthe formwork system can be individually adjustedor re-shaped to new geometrical requirements.When the concrete is sufficiently cured the doublesided vacuumatic structure can easily be takenapart and re-used.

In case of the self-supporting closed formworksystem (figure 9c), a closed vacuumatic structure actsas a self-supporting formwork structure in which theconcrete is poured. Not only the overall shape of thestructure can easily be adjusted to new requirements,also the surface texture can be retrofitted to newdemands. The materialisation of the skin and filling ofthe vacuumatic structure largely determines its load-bearing capacity.

Several preliminary tests of the different types

of formwork systems have already been carried outat the Eindhoven University of Technology and thepotential of each individual system has beenillustrated. The flexibility of vacuumatics 3D-formwork systems enables a wide variety of "free"forms (figure 10). Furthermore, the identity of theformwork systems is preserved by the curedconcrete, revealing the shape and configuration ofits filling material. This enables the production ofcustomised and even personalised surface textures(figure 11). Also folds and creases of the skinmaterial are perfectly preserved by the curedconcrete, which contributes to the vivid sensorialexperience of customised designs in concrete(figure 12).

Conclusion and Outlook

As a solidified liquid concrete has the amazingability to reveal the specific characteristics of itsformwork system. This unique material quality

Figure 10: "free" Forms in Concrete

Figure 11: Customised Surface Textures



Figure 12: Creases and Folds in Concrete

enables us to create "new" and dynamic shapes inconcrete. Considering the fact that themanufacturability and the adaptability of the concreteformwork are the limiting factors with respect to thecreation of complex geometries in concrete,vacuumatics 3d-formwork systems provide an idealsolution. The re-usability of vacuumatics contributesto an economical and sustainable manufacturing ofcustomised concrete architecture.

Our research aims for a fundamental understand-ing of the structural and geometrical behaviour ofvacuumatics 3d-formwork systems by combiningsystematic theoretical and experimental research.We see great potential once their application isfully promoted in collaboration with the latestdevelopments in concrete technology, like UHPC,FRC and SCC.

References

Gilbert, J., Patton, M., Mullen, C., Black, S. (1970), "Vacuumatics",4th year research project, Queen's University, Department ofArchitecture and Planning, Belfast (IRL).

Huijben, F., Herwijnen, F. van, Lindner, G. (2007), "Vacuumatic pre-stressed flexible architectural structures", III International Conferenceon Textile Composites and Inflatable Structures, Structural Membranes2007, Barcelona (ESP), p.197-200.

Huijben, F., Herwijnen, F. van (2007), "Vacuumatics; shaping spaceby 'freezing' the geometry of structures", International Conference onTectonics, Tectonics: Making Meaning 2007, Eindhoven University ofTechnology, Eindhoven (NLD).


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Vacuumatics 3D-Formwork Systems: Customised Concrete