Have you ever wondered what buildings would be like if they were designed by Apple or made by BMW? What if buildings had the sleek design and efficient performance that we expect from a modern phone or car?
Today's aerospace, automotive and consumer goods industries make extensive use of highly integrated digital design, computer-controlled machining, moulding, forming and most recently, 3D printing techniques. This is because they have high performance materials such as polymers and metal alloys at their disposal. These materials and their processes bring about precision and tolerances not normally possible in mainstream construction because they are expensive to form at construction scales. This is something that Freeform Construction is looking to change by developing high-performance, technical 'freeform' α-gypsum products and processes for construction automation.
Here Global Gypsum Magazine's Peter Edwards and Freeform Construction's Rupert Soar jointly explore what might occur in the next phase of offsite construction. How might buildings become more sustainable, environmentally-sensitive and more beautiful than buildings seen before?
Current building practices adopt a well-established, multi-layer system, in which the external structures, internal finish, insulation, fixtures and fittings are added sequentially. Whether conducted in a factory or directly onsite, this process allows a number of standardised planar or columnar components to be combined to build structures of varying shape, size and complexity in a step-wise manner. However, it is also a time-consuming and inflexible process that can be wasteful in terms of the materials used.
The subsequent installation of services such as water, gas, electricity (and modern additions such as telecommunications systems and energy-generation devices), add additional steps that must take place separately from each other. This can jeopardise the intention of the original design.
What if all the service and utility components of a building were integrated into the process of making walls, floors or ceilings simultaneously? In existing construction, this proposal would have trades people falling over each other, but get a machine to do it and all sorts of possibilities emerge. If one looks at what some of the leading architects are currently designing for automated construction technologies, one sees buildings that not only look organic but may even function in the same way that nature does. Today's homes cannot do this.
Inspiration from natural systems
When humans construct houses we feel that we must isolate ourselves from the outside world. We assume the outside is never 'comfortable', whereas it quite commonly is. When it is not 'just right' outside, we put extra clothes on or take them off.
Modern homes do not do this. The current paradigm involves wrapping our homes in a plastic sheet and then a massive blanket. This is like walking outside on a pleasant afternoon while wrapped in bin liners with a ski suit over the top for good measure. We are wrapping and sealing buildings in order to save heating or cooling energy (and costs). This is fine, except that buildings can't shed the extra layers when it gets hot or stuffy inside.
Building envelopes, like clothes, need to breathe and also retain a constancy of moisture, fresh air and temperature. 'Nature' understands this dilemma and constructs buildings which buffer their inhabitants against changes in external conditions. Birds construct nests from sticks in such a way that provides not only structural rigidity but also insulation. Bees and wasps must satisfy security, ventilation, temperature and moisture, not at a fixed constant level, but at a level which fluctuates around a comfort point. Some termites go to enormous lengths to satisfy many components of 'comfort' within a constantly changing external environment.
Growing homes
It is interesting to imagine what a system would look like if nature 'grew' a house for us. All the functions would be intricately connected and integrated deeply within the structure and the building would literally be an extension of our own biological function. Materials would be folded at little cost into tubes, ducts, membranes, absorbers and radiators to increase their performance, because in nature it is cheaper to fold materials than add materials. Digital design and construction can bring this to our homes - the ability to use materials sparingly because they are folded around functional components.
Proof of concept
Folding and permeating a building envelope, to increase its performance is not the exclusive domain of computers. Indeed it has been attempted using traditional methods with remarkable results.
Most notable is the Eastgate Centre in central Harare, Zimbabwe designed by Mick Pearce.2 Pearce worked closely with the engineering firm Arups to produce a unique solution unlike any before. On the outside the Centre looks like any normal office and retail centre but move close to it and one can see that the surface is intricately folded and permeated by thousands of channels that run through the building to a central atrium.
The building has an enormous surface area, which gives it an incredible ability to absorb heat from the environment and radiate it back into the air at night. By doing this it maintains a comfortable temperature range inside while the outside temperature fluctuates between 5-30°C. The blocks from which it is constructed consumed 10-20% of the total energy that it would have cost to artificially ventilate the building by using air-conditioning.
Not only did Pearce mimic the permeated surface of a termite mound but he went as far as to build the structure like termites. Pearce worked directly with the engineers and builders to form and mould the thousands of cast concrete channels and ducting components which were required to create the permeated solution, modifications were built into the design as the building unfolded, so that they could assess the building's performance. The developers literally grew a building, unique to its location, as nature would have done.
Digital design for digital construction
Rupert Soar at Freeform Construction and Mick Pearce share an interest in termite mound construction and the implications that arise. Both realise the limitations of merging the process of design and building in conventional construction as restrictive, but not when it is done in the digital domain.
Linking digital design to digital fabrication is commonly termed computer-aided design/computer-aided manufacture (CAD/CAM). CAD/CAM is being implemented in some construction automation factories, but its uptake in the volume offsite construction markets is limited. Its potential, however, is enormous.
"There are many factors that limit the implementation of automotive and consumer goods manufacturing methods in the construction industry," explains Soar. "Putting aside the differences in how the product is sold, its lifespan and the distorted sense of value placed on existing buildings, breaking into volume freeform construction could open up new opportunities."
Soar envisages producing buildings with shorter life-cycles (analagous to car or consumer products) but with 'design for disassembly', new energy saving technologies and recycling built in. "Shorter life-cycles allow a new generation of product to be built with greater performance in each iteration. Ultimately, I can envisage buildings that will have a 'digital deed' from which new versions of the building or modifications can be generated, custom fabricated and slotted into the existing structure. Anything that comes off the building would be instantly recycled back into new product as it is fundamentally a single material folded to perform multiple tasks".
If such visions can be realised they would have radical implications for the manufacturing process. Soar continues, "For digital construction to come about we will need new materials, new processes and new design tools. This will give rise to a host of new opportunities and markets".
Invisible architecture
Some architects are already designing buildings to this end. James Gardiner of Faan Studio in Australia recently worked with Enrico Dini, the innovator behind the
D-Shape process (see following page), to produce designs that go far beyond anything that today's off-site construction methods are capable of.
In their 'Villa Roccia' design prototype, Gardiner and Dini were asked to reflect a design that responded to the natural environment of the locality of Porto Rotondo in Sardinia, Italy and specifically to the rock formations of the region. Gardiner's approach strikes a balance between the constraints of the D-Shape 3D printing process and actual optimisation processes from nature, made possible with new digital design tools.
Gardiner's design process used the same 'Aeolian boulder erosion' process used to shape the boulders in the region, but speeded up to produce the overarching structure and penetrations for things such as doors and glazing. He then used a 'bone trabeculae optimisation' process to generate the complex structures inside the walls. This process gave rise to a structure that maintains strength at a significantly reduced mass while using just a single material.
What comes out of this process could be termed an 'invisible architecture', a design process that appears to have emerged through thousands of years of growth within nature itself.
A new generation of materials
If construction is to adopt manufacturing automation for volume housing markets, what are the next steps? Soar responds, "If we were talking about manufacturing 50 years ago we would have only had two options; either high-volume mass production or low volume custom production. Interestingly, in construction, it is not much different today. Digital automation brings along a third option, which gives the flexibility to manufacture custom products at volume scales. Within offsite construction, this is now completely viable and has the potential to bring about the brand identity that so many have speculated about".
So is this happening for Freeform Construction? "Not yet," says Soar, "We are currently pursuing two routes. The first is to work with the construction industry to identify the entry points for digital fabrication. The second is to develop the tools, processes and materials that they will require."
When asked if this is taking on a lot, Soar answers, "In this economic climate, it is difficult to sell an enabling technology unless manufacturers can see examples and it is difficult to promote to manufacturers without a competent understanding of the technology and materials being proposed."
What material?
Soar believes that, unlike in other sectors such as the automotive industry, materials that are as flexible, formable, machineable, printable, accurate and recyclable as metal alloys and some polymers, do not yet exist in the construction sector.
Soar says that the key is in controlling how a material goes through a phase change, i.e. a material's change from say a liquid to a solid. At construction scales the two most common candidates for this task are concrete and gypsum. Both use a combination of calcining and then hydration to initiate a phase change but this process is rarely fast. Soar sees this as a problem.
"Concrete and gypsum have additives to slow their set rates for good reason. Part of this is that they need to be left to set in a form and the other is the issue of exothermic heat generation when constructing large sections. In automated processes the idea of adding water to a metal or a polymer before it goes in a mould, would seem ridiculous, but there is a middle ground. This is to modify construction materials so that the phase change can be activated and regulated."
Existing technologies
This challenge has occupied enormous efforts from those groups engaged in construction automation processes and there are currently just three construction-scale 3D printing processes in existence:
Contour Crafting: Contour Crafting, a US-based company, uses a modified rapid curing cement 'mortar' to form a quick setting freeform shell, which can be backfilled with concrete. Contour Crafting's 'skin and core' approach overcomes the exothermic issues of the rapidly curing mortar, which is extruded and shaped simultaneously with a trowel.
D-Shape: D-Shape is the only large format process that uses a principle from mainstream additive manufacturing. It involves laying down a bed of dolomite powder and using an oversized inkjet printing boom to selectively deposit an activator fluid. The result is a clean and very hard magnesium oxide cement.
Concrete Printing: Concrete Printing is a paste deposition process that uses a modified 'high build' OPC/blast-furnace slag blend. It was Concrete Printing which Soar first began work on in 2005. "One of our objectives with the process was to use 'off the shelf' components and materials," says Soar. "It was not so much about what to print, but how to print it. The focus was on concrete, but concrete likes to be cast and sets slowly in a form. It also requires modification and control between batches".
Gypsum as a material for digital construction
What ultimately led Soar to establish Freeform Construction was the need for a 'selective cure', printable material where recycling, finishing and green credentials were inherent.
Three years of research resulted in gypsum being selected as the chosen material. Gypsum is not routinely associated with high-performance by the construction industry, which generally considers it as the main component of wallboard, locked away between sheets of paper or card. However, in 'low volume' sectors, α-gypsum is regularly used for high performance manufacturing methods such as casting of dental components, metal prototyping and ceramic wares.
Soar began with the premise that gypsum has a long history as stucco, architectural reliefs and even statues. In the 19th century, materials such a Keene's cement were commonly kneaded and rippled to form marble substitute: these materials could be finished to very high standards and exhibit very high performance and durability, even outdoors.
Before the advent of wallboard, cast gypsum blocks formed the backbone for partitioning systems in the west, where straw was commonly mixed with gypsum to form a composite. Gypsum blocks never went away and continue as low risk, low volume market penetrators for gypsum in emerging markets but they suffer the negative perceptions that go with 'wet trades.'
Soar's goal was to discover if these materials would fit right into a modern digital manufacturing environment. "One of the overarching requirements..." says Soar, "is that the material must be selectively curable within five to 10 minutes and produce large-scale construction components such as freeform panelisation and cladding systems with extremely fine finishes and tolerances."
"For example, these materials open up markets for freeform interiors where a single continuous marbled surface could be custom installed based on a digital scan of the space they are to be placed within. Imagine walking into a marbled bathroom and finding not a single edge or visible joint, but just a continuous polished surface flowing from the floors, walls, bath, sink and shelves. If the time comes to replace it or modify the structure, there would be a digital back-up of the space from which to generate new tiles or panels from. With gypsum as the material, all of this could be done in the knowledge that the product is 100% recyclable and linking digital scanning to digital design and digital construction will bring about large scale design-for-assembly and disassembly to construction for the first time."
Soar is aware of gypsum's limitations and says, "Our research has demonstrated that triggerable, high-density α-gypsum materials do not exhibit the water absorption and solubility issues associated with β-gypsum products. We can produce gypsum materials with less than 5% absorption and very low levels of solubility without additives. However, we have some way to go to validate the material for both structural or external application. Crucially, our work has shown nothing that suggests that this isn't possible."
Whereas the cement-based 3D printing processes are looking at the primary and secondary structure of a building, Soar believes that there are markets for high-performance, high-tolerance materials that could satisfy markets for partitioning and freeform interiors.
MineralJetTM and MineralStoneTM
Freeform's current business model is as both consultant and developer. As consultant, it informs companies and organisations on digital integration and digital fabrication techniques. As developer, it is ready to 'jump in' with collaborators by generating new intellectual property or bringing its own intellectual property and a research capability around the processes, materials, applications and design tools that the industry is looking to.
The company has registered patents for three aspects of its business model. One is the high-density triggerable α-gypsum material called MineralStone, one is the large format 3D printing capability known as MineralJet and the third is a novel passive ventilation system based on termite mounds.
The approach taken with MineralJet was to break down the device into its constituent parts, i.e. the material delivery system, the movement of the deposition head within a 'build envelope' and the deposition device itself. By breaking down the process into modules, Freeform was able to separate the components and make each one interchangeable. This meant that it did not have to fix the type of placement device required, as part of the cost package. The deposition head could be interchanged and applied to any gantry or articulated robotic unit.
The implications of this are that where a rigid gantry frame device is good at building components within its build envelope, an articulated robot can work outside of this envelope. In other words, you could roll an articulated robot into a space and have it deposit material directly onto the existing walls and ceilings of a room.
Using conventional systems and materials, such a system would have a resolution of around 3-5mm, which is fairly rough. However, the high density gypsum material, known as MineralStone™, that Freeform has developed for the process, can be machined with standard cutting tools to a very high tolerance. By making the deposition head interchangeable, it can be swapped for a high-speed cutting head to finish a component to a polished finish.
Soar notes, "The key is the material. It's not about getting the material to phase-change instantly, it's as much about preparing the material to control its rheology. MineralStone is a strange material in that it exhibits shear thinning and then shear thickening properties under certain conditions. This is set up in the deposition process. What this means is that the material will allow us to build upwards and outwards while it is technically still 'wet'. Doing this allows us to activate the cure within minutes, not seconds, so we can control the exothermic reaction and hence the integrity of the object."
So will we be seeing this device soon? Soar responds cautiously, "MineralJet shows that we have a capability and experience. Currently, it serves us to have the intellectual property for such devices and materials which we can form collaborations around. At the moment our role is consulting to the construction industry to target applications around which we can develop processes and materials." Freeform appears to be positioning itself for a tipping point and it is revealing to see where it thinks the entry points for these products are.
Controlling the phase-change
The MineralStoneTM material is being developed on more than one front. Historically, controlling the gypsum phase-change has received considerable attention, but it is important for Freeform's clients to know that they have access to unique intellectual property that will be used to develop the material around new applications. MineralStone™ has interesting properties, it produces a material as strong as concrete yet it produces fine marble-like parts.
From the outset, Freeform wanted to move away from powders and mixing and instead moved towards the supply of specific blended retarded pastes. This reduces airborne particulates and allows the paste's rheology to be controlled before it is delivered.
At its core the material had to have certain properties that make it phase-changeable with an input of energy. This is achieved through a combination of Freeform's chemical activator system and the behaviour of the material as it passes through the deposition head of the fabrication process.
Most remarkable are Freeform's claims that it can achieve this with a water ratio at or close to its stoichiometric point, i.e. the point at which hydration occurs. The implication of this is that little post-drying is needed in the material. An added benefit is that the material produced is very fine and very dense (~2400kg/m3).
The Plank(TM)
As part of Freeform's co-development work with MineralStone, it has teamed up with a specialist machine producer to develop inorganic lightweight 'skin and core' products. To date, these have been embodied in The Plank (Figure 2), which is a conceptual building system that demonstrates the capability of the process Freeform is collaborating on.
Making gypsum froths is not new, but integrating them as a low density, high strength, 'skin and core' systems is new. As Soar explains, "The process we are working on combines MineralStone's high density polished marble surface with a structured high strength gypsum foam core, as a single operation and single material solution. In this instance, if we used generic low strength gypsum foam, with a hard polished MineralStone skin, we would struggle to achieve the minimum safe working loads for such a product. Therefore we had to go further to find a solution allowing us to structure the internal core to maintain its strength while reducing its mass."
If The Plank can be realised, Freeform's process would move beyond conventional batch-produced gypsum block production to a continuous method for generating Planks for refurb, full partition panels or beam and block flooring systems. The novel approach integrates a machining stage to produce the high tolerance fit and a fine surface finish that would eliminate the need for secondary skim-coating.
In addition, machining and routing would allow rebate details such as door frames to be integral to the product. "The Plank was designed to promote discussion and collaboration around the emerging problems of disassembly and of reconfiguring spaces during building retrofits within very short timeframes (sometimes less than five years)," says Soar.
As a partition system, The Plank would come in 150mm x 2500mm x 350mm sections that could be lifted and fitted in a single-worker process and slotted together using a 'tongue-and-groove' system. The structure combines structural rigidity and insulation while meeting standard tests such as pull-out and impact. Simple changes to the finishing process could allow for custom murals to be printed into the surface and textures to be applied. Soar believes that The Plank could offer an alternative to the increasing reliance on polymer foam systems and the peace of mind which goes with this.
Looking further ahead
Currently, there exist in the world only two (non-hydro) chemically induced construction-scale selectively curable phase-change materials. These are the D-Shape MgO and MineralStone systems, but this is only the beginning. It is worth noting that even though these materials offer a step change to the capabilities of those who will exploit them, both materials can be sourced as by-products and both have green credentials beyond traditional cement and concrete.
Automation of the 'wet trades' is here. What will emerge from processes where complex curves, textures and forms cost no more than making something cubic? What other capabilities will emerge for our buildings which we have not dreamt of yet?
Think of what could be done by simply combining these first two materials into a digital construction framework, one for say, structural components and one for cladding components, or one for internal and one for external applications. We can only wonder what this will mean for our homes and other buildings. If we look at the advances 3D printing is making in the automotive and consumer goods sectors, then integrating ducts, services and high tech components could go hand-in-hand with responsible manufacturing and sustainable construction.
Construction is often described as lagging behind these sectors in its use of technology, but it is clear that this technology is ready to make an impact and deliver a supremely competitive edge to an industry that could so easily delight the largest market segment of them all – the homeowner.
References
1. Images by James Gardiner, Faan Studio, Melbourne, Australia. Reproduced with permission.
2. Miles, P.; 'Inspired, naturally,' Financial Times website (UK), 12 August 2011. (http://www.ft.com/cms/s/2/37bb18a2-bea7-11e0-ab21-00144feabdc0.html#axzz1V1XdYXl6).
