Pour 2

The second pour was also a success-creating an inverse mold of my first pour. I basically just flipped the first assembly and poured into the frame that had the fabric attached to it and then cut the fabric away. Using less petroleum worked fine and it left a surface more related to the fabric texture than the texture created by the jelly as on the last pour. I also used a different material-Quickcrete rather than Cement all, which didn't settle as well, giving the surface a more porous quality. The idea that you can make one casting and then just cast off of previous castings is really efficient and the cloth can be reused several times in the process, significantly reducing the amount of waste materials. Below are some photos of the process: the first of the two frames assembled, the next of the concrete poured inside the frames, and the last of the two pours and fabric formwork.

The First Pour

My first fabric formwork pour was a success! Using three assembled pieces, I was able to create a concrete that molded to the fabric between support points. The assembly had three pieces-a base on which the support points were glued, a lower frame over which the fabric was stretched tightly and a third frame into which I poured the concrete. To make sure the concrete wouldn't adhere to the fabric I applied several layers of spray shellac as well as petroleum jelly to the fabric. On the next pour I might not apply so much petroleum as it did affect the surface texture even if it made it very easy to pull the concrete away from the fabric. My next step is to make an inverse mold of this mold but stretching the fabric over the already poured concrete and pouring new concrete over that. Below are some pictures of the process. The first is the three frames unassmebled, the second the assembled frames with the concrete poured, and the last the finished product.

Forming Flexibly

My original interest in concrete formwork led me to find the curious idea of fabric formwork, which is being developed as an efficient and “green” alternative to traditional formwork options. Developed primarily by an entity known as CAST (The Center for Architectural Structures and Technology) at the University of Manitoba, fabric, primarily geotextiles commonly used in road construction, is being used as a formwork that gives architectural beams and columns a more efficient shape, cutting down on the amount of material used than when creating more traditional-shaped pieces. The results are beams that look almost exactly like a moment diagram of the concrete-deeper at locations with more stress or strain, slimmer at areas under little strain. Not only is the shape the most efficient use of the material, but the shape itself is elegant and appears natural due to its basis in mathematics and physics. To the human eye, it just makes sense.

Fabric formwork also gives the finished concrete a level of strength not given by other formwork due to the filtering that occurs through the fabric. The porosity of the fabric allows air bubbles and extra mix water to filter through the formwork membrane. The formwork itself is also very lightweight, inexpensive, and, due to its flexibility, reusable for multiple castings.

Aside from the efficiencies that can be produced in structural concrete members, fabric concrete also provides flexibility in design for architects, allowing them to create a variety of forms otherwise impossible with more orthogonal formwork types. The shapes created by fabric are tensile geometries, something that would be hard to obtain in concrete, a naturally compressive material.

One of the main architects exploring the possibilities of fabric formwork is Kenzo Unno, who uses fabric formwork to obtain both an efficient use of material and certain aesthetic desires in his work. In his research, Kenzo Unno was able to create a “zero waste” wall assembly into which the concrete is poured and the only piece that is then removed is the fabric formwork, which can then be reused for another casting or as an earth stabilizer. A diagram of the wall assembly can be seen at the right. The linear wood pieces on the exterior become battens onto which the exterior cladding is applied. These wall assembly pieces can easily be constructed off-site, and then dropped into place on the construction site.

Aesthetically, Kenzo Unno has done a lot of cast-in-place walls in fabric formwork, giving walls a soft, pillow-like surface, and again reducing the amount of material wasted during construction. His cast-in-place walls have come in two forms, one known as the frame method, the other as the quilt-point method. The frame method uses a series of vertical restraints in between which the fabric is stretched and the concrete poured. The quilt-point method uses a series of ties in the walls between which the fabric is stretched and the concrete poured. The concrete is vibrated externally by poking the wet concrete contained by the fabric with a stick and, as in the case of the quilt-point method, the fabric being stretched by the concrete forms into its natural tension geometries, allowing it to be entirely self-sufficient structurally.

Fabric formwork has also been used to create precast concrete panels in a variety of forms. The method for producing these forms is simple-first a rectangular frame of the dimensions of the final panel is laid down inside of which intermediate supports are placed (these supports will retain the fabric at these points and the fabric will in turn bow between them). Next, a pre-tensioned fabric membrane is placed over this frame, on top of which an upper frame that will contain the wet concrete is placed. This frame will determine the edge thickness of the panel and inside of it any reinforcement can be placed. When wet concrete is poured into this assembly, it causes the fabric to deflect downward creating three-dimensional tension curves between the designated support points of the base frame. The castings created from this method can then in turn be used to create inverse castings by pouring a new casting along its surface on top of a layer of fabric.

The implications that this research has on the future of concrete as a building material are huge. Not only is it efficient in how it uses materials in construction and creates a strong product through the filtering process, but it provides an aesthetic to concrete previously unavailable. I like that the fabric formwork uses the properties of wet concrete to create its form. Instead of trying to contain the wet concrete, it works with what it naturally wants to do unlike many other types of formwork, allowing what is seen as a “difficult” property of the material to become its driving force. The next step will be to test some of these processes myself-specifically the precast panel construction method-on a smaller scale.

What aspects of this research will translate into the warming hut is yet to be seen. I definitely like the idea that using this formwork will allow for less waste as our hut is located at the top of a very steep mountain side and so to have a lot of waste due to construction would be very inefficient indeed. I also think the efficiently shaped beams that give a very natural form to the architecture is something I think I’d like to apply to the warming hut. Let’s see what the castings help me discover.

References:

"CAST :: Fabric Formwork." University of Manitoba. Web. 23 Jan. 2011. http://www.umanitboa.ca/cast_building/research/fabric_formwork/index.html

Miller, Anne. "Concrete Dreams." Canadian Architect (2008): 71-73. Print.

West, Mark. Kenzo Unno Fabric Formed Walls. PDF.

West, Mark. Prestressed Fabric Formworks For Precast Concrete Panels. Centre for Architectural Structures and Technology. PDF.

West, Mark. "True to Form." Canadian Architect: 54-56. Print.

Measured Object Excercise

A throwback to 1st year, my measured object. I really enjoyed this exercise as it was nice to hand draw something for a change.

The Warming Hut

Starting off studio with a small design problem-a warming hut for skiers that incorporates the complexity of a steeply sloped site and the complexities present when designing with concrete. When looking up precedents, one theme came through pretty strongly-the idea of centrality. Most warming huts are organized around the stove or fire, which makes for an efficient transfer of heat to many people but also provides the perfect place for people to gather and talk.


I see the warming hut being a very welcoming place on the side of this large, frosted mountain. In a landscape that can seem pretty forbidding to humans, the warming hut should provide a sense of comfort just upon sight. It is why I chose to nestle my warming hut in a nook of sorts of the mountain-a place where the land almost folds back in on itself, which would allow the warming hut to be almost embraced by the mountain. Most warming huts do this when they're constructed of materials that inherently provide that sense of warmth, like wood, however, with a concrete structure, this could prove to be a challenge. To me, concrete has always seemed to be a fairly cold material, institutional almost, so the challenge will be to make concrete friendly and inviting. Almost the exact opposite of this idea is the image seen here-what seems to be almost an ice fortress on the mountain that looks like something from out of the Lord of the Rings. While uninviting, it does have its place on the mountain and it fits in almost perfectly with the bulky snow peaks and tall evergreens surrounding it.