_Thinness_2.0

Introduction

THINNESS is a collaboration between Syracuse University School of Architecture professors Julie Larsen and Roger Hubeli (partners of Aptum) and the Cemex Research Group (CRG), the research arm of the 2nd largest cement company in the world, to develop a 10’x10’x10’ tall lightweight modular concrete pavilion (figure 01). The goals were to develop a lightweight modular concrete pavilion as a design research project that is a testing ground for interdependencies between digital architectural design and advanced concrete technologies to redefine the typology of a cross-vault.

Veiling Concrete

Like much of today’s culture, architecture is driven by a fascination for the ‘thin’. ‘Thinness’ is situated within this tension by hybridizing veneer and structure and creating a novel approach to being ‘thin’ through the use of modern ultra thin, high-performance, lightweight concrete. Using the development and construction of a transportable concrete pavilion, the project serves as a testing ground on the interdependencies between processes of digital fabrication, tectonic aggregation and architectural expression generated by concrete elements that aggregate into a space that is comprised of 16 elements that form a cross vault like structure. The goals were to design the cross-vaulted pavilion out of a thin concrete veil while still maintaining structural strength and integrity in the form, as seen in the interior view.

Methodology

Using the Thinness pavilion as a case study, the typological versus the topological outcome is developed through a design methodology that advances a material and its formal expression through an iterative approach. We were in search of a structured translation of the material into a specific formal and spatial result. The typology of the cross-vault is explored through its materiality and assembly leading to a unique casting method and specific concrete mix, newly conceived for the pavilion. To explore innovative potential of a material through a typology, the design methodology is turned inside out.

Structural Development

The intent was to transport the pavilion to reflect its temporal qualities and a need for lightness, requiring a structural shift from mostly compression/ buckling to bending stresses. Therefore, the elements were optimized to carry load in their upright and horizontal position and for easy mobility each element only weighs 200 lbs/91 kg. The concrete mix, with extremely fine aggregates, results in high performance concrete with high strength and a lightweight density (87 lb/ft3 / 1.4 kg/l in comparison to 87 lb/ft3 / 2.4 kg/l for ‘standard’ concrete) allowing for much lighter and thinner elements. The hollowed out, vaulted modules made of thin, ½” walls was only achievable because of the high strength of the concrete surfaces to perform at a higher capacity than typical concrete.

Crafting the Digital

In addition to the thinness and density of the material we also studied the material’s capacity to be thinned-out by puncturing the surface with voids that followed both the bending moment diagram during the horizontal position and the compression in its upright position. Besides making the elements lighter, this offered another form of testing the concrete's capacity to become seemingly transparent. In order to accentuate the fact that the surface held the strength, the pattern needed to respond to the stress and load patterns of the surface as the pieces are moved. Initial structural moment diagrams were made to test where the highest stress was located on each piece. The arc of the structural diagram informed where the pattern in grasshopper became denser to ensure that the load distribution would be reduced. The pattern was generated with a digital technique in grasshopper similar to ‘diffusion limited aggregation’ as a way to distribute the voids in denser areas needing less material. But instead of using the script to generate mass, it was used to distribute voids in a web-like configuration that connects and follows the stresses. It was at this stage, that we realized the ideal scale of the voids was not ideal for the concrete mix because the Cemex Resilia™ mix required 17 mm steel fibers but the mass between voids in the surface were only 15mm. The decision needed to be that either the pattern, form, or mix change scale to accommodate the design ambitions. We decided to change the mix and reduce the size of the steel fibers, which didn’t exist prior to the project.

Fabrication

The formwork is a combination of state of the art digital fabrication techniques with water jet cut silicone in-lays along with the prehistoric technique of ‘lost wax molds’ using silicone and wax formwork that is melted and reused after each pour. The wax gives the flexibility to design complex forms with a limited set of formworks (3 in total were needed for 16 elements). The matrix of the mix, the additives, as well as the fiber reinforcements were continuously adapted to the development of the form and vice versa.

First, an inner and outer steel form was made and later braced on the outside with steel angles for additional rigidity. To make the pattern, water jet cut sheets of costume poured silicone sheets were applied to the interior of the steel form to cast the inverse in wax. Wax was used for the interior formwork so it could be melted away after each concrete cast. The wax was melted in drums and then poured into the silicon-clad steel formwork. The columns of wax were poured and then the silicon was peeled away to reveal the wax column in its entirety. Each column of wax was then melted away with large, tube-like heaters running the length of the columns.

Research Assistant: Sean Morgan