September 14, 2006

CENTRE OF ARCHITECTURAL STRUCTURES AND TECHNOLOGY

Tests of cast trusses were completed in a lab before the fabric forming concept is taken onto a construction site. Developers explored various design concepts in order to showcase fabric formwork’s flexibility.

Innovation

Fabric forming opens up creative possibilities

Casting concept earns developers a Holcim Award

FAZEENA SAMAD

staff writer

TORONTO

Fabric formwork may soon break the mold when it comes to concrete casting in the construction industry.

Fabric forming, which uses a flexible textile membrane in place of traditional box molds, is a revolutionary approach to concrete casting that promises greater design detail, potentially stronger structures, and reduced construction cost.

According to Mark West, director for the Centre of Architectural Structures and Technology (CAST) at the University of Manitoba, fabric forming has the potential to replace conventional rigid molds and to allow for more efficient and beautiful structures.

“Architecturally, it offers a whole new universe of sculptural and structural form; quite simply, flexible formwork transforms cast concrete from a hard and even brutal material into a soft and sensual material,” he explained. “That’s a pretty good trick, and it is accomplished more or less effortlessly by a combination of materials ; wet concrete and a flexible tension membrane.”

The project team developed fabric formwork out of polyolefin geotextiles, a material commonly used to make plastic tarps, for concrete forming in a variety of above-ground construction settings, including column walls, beams and slabs in both precast and in-situ construction.

“Our most recent work offers methods of fabric-forming cast-in-place walls and columns that use only conventional procedures as well. Full-scale trials of these methods will take place in Winnipeg this fall,” he said. “This method allows in-situ casting of complex, beautiful, and efficient columns and walls using standard wall-form methods, materials, and tools.”

West, recipient of the Bronze 2005 Holcim Award for his innovative work and research on fabric formed concrete, hopes the industry embraces fabric formworks, not only because of its construction benefits but also because it has the potential to change the way buildings are designed.

“I am excited by the interest generated globally in widely different building economies,” he said, commenting on the Holcim Award. “I would love to see this developed in India, Africa and the Mid-East for example, and the Holcim Award has given us correspondents and collaborators in these regions.”

The material used is relatively inexpensive, making it accessible to both high and low technology-building cultures. The economic advantage to using fabric formwork is derived from the material’s light weight and its reusability characteristics.

CENTRE OF ARCHITECTURAL STRUCTURES AND TECHNOLOGY

Forming on site is made easy with the use of fabric, which is so lightweight and manageable, it’s child’s play.

“From a construction economy point of view, there are both proven and potential savings to be gained. The success of commercially available fabric formwork products demonstrates material and time savings offered by this technology,” West explains. “The material savings are definitely there. It is a well known engineering fact that the most efficient way to resist a force is through linear tension, and this is precisely what a tension membrane accomplishes.”

West also noted that fabric formwork is the best way to approach sustainable construction, because it simply uses less than conventional formwork technology, which has not “significantly advanced since the introduction of plywood after World War II.”

In terms of sustainable building practice, it is a “low hanging fruit,” an old and inefficient building method.

The use of fabric formed concrete could also potentially extend the service life of the structure by producing a higher quality of concrete. Permeable fabric used in the forming process allows excess water and air bubbles to bleed through, producing an optimal mixture of water/cement ratio, thereby leaving a bug-hole free, cement-rich concrete at the surface of the cast, West said.

In addition to his work on fabric forming, West and his team (Christopher Wiebe, Phillip Christensen and Fariborz Hashemian) have been credited with producing the world’s first reinforced concrete beam cast from a pre-stressed fabric mold, formed with a single flat piece of geotextile material.

Currently, West is trying to “address the problem of the learning curve” most builders face when it comes to new techniques.

“The nature of the construction industry makes it very difficult, if not impossible, for builders to stop and train themselves to use a new technique or technology, particularly if the technique is new and commercially unproven. Adopting a new method presents an unnecessary risk so long as the old ways are making reliable money,” West explained. “There is nothing here any good builder doesn’t already know how to do. The invention simply offers a recombination, or collage, of existing conventional procedures.”

Print | Email | Comment