By Mark West
The Centre for Architectural Structures and Technology is an architectural research lab at the University of Manitoba that seeks new boundaries for architectural thought, design, and building technology through physical explorations of materials, tools, and methods; the study of natural law; and the free play of imagination. A wide range of methods for research and creation are used together at CAST, mixing traditions of fine arts, engineering, and architectural design. Presently there are two major areas of research housed at CAST: flexible formwork for concrete construction and digital fabrication/dynamic systems.
The CAST building was specifically designed and constructed to support hands-on research-creation. It is located next to the faculty of architecture’s graduate studios, across the street from structural engineering labs, and near the School of Fine Arts studios. It contains and combines wood and metal shop facilities with studio space, a strong floor and a hydraulic actuator for structural testing, and a nice big sound system. The CAST lab is not an engineering lab, nor is it a building science lab, though we are engaged in both of these fields. It provides a space for engineers, architects, and artists to find new ways of working.
The use of flexible fabric formwork in the construction of concrete structures and architecture is a new field of academic research and an emerging construction technology. The simple act of replacing conventional rigid formwork molds with a flexible fabric membrane opens up so many new opportunities for design, construction, and engineering that it constitutes a deep and fundamental change in construction technology. Inventions found and developed in this area at CAST include methods for efficiently forming concrete columns, walls, beams, T-beams, trusses, slabs, vaults, and panels. CAST-based construction projects include contributions to buildings in Winnipeg, Puerto Rico, and Chile. CAST-inspired research has also contributed to constructions in the UK.
In terms of economy and sustainability, using fabric as a mold can cut the amount of material used in formwork construction by one or two orders of magnitude (tens to hundreds of times less). The efficiency of fabric molds comes from the fact that they function as tension membranes—the single most efficient way to contain volumes under pressure (in this case, wet concrete). Nearly any fabric can be used, though we usually use woven polyolefin fabrics (coated or uncoated), which are widely available, very inexpensive, strong, tough, and reusable. Permeable geotextile fabrics produce excellent surface finishes and very high-quality concrete due to their filtering action, as they allow air bubbles and excess mix water to bleed through the mold wall, leaving a cement-rich paste at the surface of a cast. Because concrete does not stick to these fabrics, form oils are never needed.
In terms of design, an entirely new world of architectural, structural, and sculptural form is opened up by flexible molds. Unprecedented and deeply beautiful shapes are produced by the three-dimensional tension geometries naturally produced by these tension membranes and the concrete they contain. Concrete is reborn as new, sensual, and sensitive material. The complex curves produced by these molds can be used to structural advantage by allowing a designer to follow the bending moment curves of a beam, for example, or by inverting naturally occurring tension geometries to produce funicular compression shells. Using fabric as a mold wall can easily produce reinforced concrete trusses, a rarity due to the complexity and cost of building truss molds. By taking advantage of efficient structural curvatures, significant savings in concrete and steel are possible. Savings in these materials also produce savings in the substantial greenhouse gas emissions and embodied energy inherent to these materials. Savings in structural deadweight of individual members cascade throughout the structure of a building, multiplying these savings for the design as a whole (particularly in foundation materials and costs).
CAST research in fabric formwork technology has spawned academic research in schools of architecture and engineering around the world, including England, Scotland, Holland, Chile, and the United States.
Fabric formwork research at CAST is dedicated to using very simple construction methods and common building materials. For example, all our inventions use only flat sheets of fabric cut directly off the roll—no geometric tailoring or complex seams or joints are used. Even sewing machines are avoided as too difficult for the world of construction. This dedication to the utmost simplicity not only ensures the buildability of these inventions, but also makes these new technologies accessible to both high- and low-capital building cultures and economies.
For the past two years, fabric formwork research has been supported by SSHRC research/creation fine arts funding. The past five years, Lafarge Building Materials Group and the Canadian Precast Concrete Institute (CPCI) have supported our formwork research through invaluable in-kind contributions. The Canadian Masonry Research Institute (CMRI) has supported our structural masonry research. The Cement Association of Canada (CAC) supports research in improved concrete quality using permeable fabric forms.