Thin is In: The Promise of Structural Concrete 2 Centimeters Thick

Mike Campos/AerialShotz Thinness comprises 12 exterior column modules and four interior light well modules

"Thinness merges craft, fabrication, and the digital realm. It’s compelling to go through the images and the researchers’ process and see how those three areas were combined." —Juror Randy Deutsch, AIA

Concrete is a wonder in many ways: easy to make, easy to form, and strong upon cure to boot. Its mass and bulkiness, however, means it can be passed over for wood or steel. But what if concrete could be rendered lightweight?

Collaborating with the research and development department of global concrete manufacturer Cemex, headquartered outside Monterrey, Mexico, Julie Larsen, Assoc. AIA, and Roger Hubeli, who teach at Syracuse University and run the design firm Aptum Architecture, explored this postulation with Thinness, a concrete pavilion that stands 10 feet tall, wide, and long, but with walls that are a mere 2 centimeters thick.

Courtesy Aptum Architecture Thinness' light wells and perforations afford a high quality of light inside the pavilion

Courtesy Aptum Architecture Grasshopper overlay of a Thinness column’s perforation pattern in conjunction with its stress map

The structure’s secret lies in its highly fluid concrete mix, which uses glass beads for aggregate and 1.5-centimeter-long steel fibers and fiberglass fibers that provide tensile strength while cutting the weight of the mix almost by half that of the conventional formulation.

Thinness comprises 12 tapered hollow columns and four skylight, or light well, units. The project’s modularity allows for easy assembly and portability while the columns are perforated to allow light into the pavilion and to cut down further on their weight—to 200 pounds each.

While architects have been pushing the structural limits of concrete for decades, much of it has been in the form of shells and arches, which work solely in terms of compression, Larsen says. Hubeli adds: “The perception of concrete [versus] the reality of its capacity is quite huge. Concrete is extremely advanced, but the understanding of the material is very limited. That gap allows for innovation.”

The pavilion’s concrete is self-consolidating and self-compacting, but the designers and fabricators still had to experiment with how the mix and its fibers would distribute themselves around the many sharp angles of the columns’ wax formwork delineating the rectilinear perforations. If the fibers clumped and intertwined, the walls would lose strength.

Courtesy Aptum Architecture Inner and outer steel forms were made and later braced on the outside with steel angles for added rigidity. Silicon was poured into the forms to create a thin layer and then water jet–cut to form the void pattern, where the wax would form

Courtesy Aptum Architecture Small-scale test of how the wax was heated and melted after the concrete cured, leaving behind voids in the concrete

Larsen, Hubeli, and Davide Zampini, head of Cemex Research Group, say the project was as much about the structure itself as it was about demonstrating the potential of interdisciplinary coordination—in this case, between academia, architecture, and concrete manufacturing. Though the pavilion is, at this stage, just a test bed, they predict that superthin concrete will soon begin to appear in conventional construction—even, in some cases, as load-bearing elements. “The material has all sorts of possibilities,” Zampini says, “but people don’t know about them.”

For example, the ultrathin concrete modules could theoretically be scaled up or stacked to create a vertical wall. “The idea,” Hubeli says, “is to make us think about an entire light building.”

Courtesy Aptum Architecture Extrapolating the potential of ultrathin concrete from pavilion to skyscraper

Courtesy Aptum Architecture Additional bracing helped prevent the steel outer forms from bowing due to the compression of the concrete on the forms

Courtesy Aptum Architecture Outer and inner steel forms support waterjet cut silicon inlays (green) against which lost-wax inverse columns (white) were cast

Courtesy Aptum Architecture The formwork combines digital fabrication techniques utilizing water jet–cut silicon inlays with the time-tested technique of "lost wax molds." The silicon was used to cast the wax form, which is melted and reused after each concrete pour

Courtesy Aptum Architecture The silicon inlays were removed from the lost-wax formwork, to be replaced by poured-in-place concrete

Courtesy Aptum Architecture The freestanding lost-wax inverse column mold

Courtesy Aptum Architecture Mock-up of how the fibers in the concrete mix will distribute around the column perforations

Project Credits
Project: Thinness
Design Firm: Aptum Architecture, Syracuse, N.Y. . Roger Hubeli, Julie Larsen, Assoc. AIA (project team)
Industry Partner: Cemex Global R&D . Davide Zampini, Alexandre Guerini, Jeremy Esser, Matthew Meyers (project team)
Research Assistants: Sean Morgan, Ethan Schafer
Fabricator: Cemex Global R&D
Structural Engineer: Sinéad Mac Namar
Size: 100 square feet