How do you shape concrete into seemingly weightless organic wisps without the use of heavy complex molds? Yarn. Miles and miles of yarn, knitted together using a brand new digital fabrication technique that might just change the face of architecture as we know it. The 3D-knitted textile technology known as KnitCrete employs an unlikely mix of cement paste, wood, fabric, balloons, and automated machinery to create structures that could help concrete break through the barriers of its own limitations.
A thin, double-curved concrete pavilion by Zaha Hadid Architects and ETH Zurich allows us to look at concrete in a whole new way. “KnitCandela” pays homage to the concrete shell structures of Spanish-Mexican architect and engineer Félix Candela, revolutionizing them for a new age using computational design methods and innovative cable-net and textile structural components known as KnitCrete “formworks.” Traditionally, formworks for curved concrete structures are made of wood. Unfortunately, those formworks are expensive to produce and transport, and they nearly always end up in the trash when the project is complete.
“While Candela relied on combining hyperbolic paraboloid surfaces (“hypes”) to produce reusable formworks leading to a reduction of construction waste, KnitCrete allows for the realization of a much wider range of anticlastic geometries,” explains the team over at Zaha Hadid. “With this cable-net and fabric formwork system, expressive, freeform concrete surfaces can now be constructed efficiently, without the need for complex molds. KnitCandela’s thin, double-curved concrete shell, with a surface area of almost 50 square meters and weighing more than five tonnes, was applied on a KnitCrete formwork of 55 kilograms. The knitted fabric of the formwork system was carried to Mexico from Switzerland in a suitcase.”
The geometry of the shell takes inspiration from the colorful traditional dresses of Jalisco, Mexico, as well as Candela’s own acclaimed restaurant at Xochimilco. The design is the result of a collaborative effort between teams in Europe and Mexico, and it was designed to be built on a tight schedule in a small space with a low budget. The experimental structure marries old and new, making sure not to discount the value of skilled human labor by “integrating digital fabrication with the skills of traditional craftsmanship and construction methods.”
The process of building the KnitCandela pavilion was actually pretty cool. It began with a support system of wood and tensioned cable-net that remained inside the finished structure instead of being thrown away afterward. Four long strips of knitted textiles ranging from 15 meters to 26 meters in length were then woven around this base in two distinct layers: an interior aesthetic surface that displays a colorful pattern, and an exterior surface that creates the structure’s overall shape. Before it was covered in cement paste, special modeling balloons were inserted into the empty spaces, producing a “structurally efficient waffle shell” of cavities inside.
The architects add: “The soft, colorful textile interior of KnitCandela’s shell and its hard, concrete exterior are visible from all viewing angles. The textile’s striped pattern expresses the knitting fabrication process and the radial symmetry of the shape. This patterning, along with the simultaneous visibility of the soft interior and the hard exterior of the shell, enhances the visitor’s spatial experience and the curvatures of the KnitCandela’s form.”