zaha hadid architects designs ultra-thin concrete shell that pays homage to félix candela

zaha hadid architects (ZHA) has constructed a sinuous concrete shell as part of the firm’s first exhibition in both mexico and latin america. the structure is titled ‘KnitCandela’, a name that — alongside the design of the pavilion — pays homage to acclaimed architect and engineer félix candela. the experimental scheme re-imagines candela’s inventive concrete shell structures through the introduction of new computational design methods and formwork technology developed at ETH zurich.

the sinuous concrete shell is titled ‘KnitCandela’
image by juan pablo allegre

constructed at the museo universitario arte contemporáneo (MUAC), ‘KnitCandela’ was built on an ultra-lightweight knitted formwork that was carried to mexico from switzerland in a suitcase. the project’s dynamic geometry not only references félix candela’s restaurant at xochimilco, but also the fluid forms of the colorful traditional dress of jalisco — a neighboring state fringing the pacific ocean.

the design pays homage to architect and engineer félix candela
image by leo bieling

ZHCODE — ZHA’s computation and design research group — was responsible for the structure’s architectural design, while block research group (BRG) of ETH zurich introduced the KnitCrete formwork technology and developed the structural design and construction system. meanwhile, architecture extrapolated (R-EX) managed the execution of the project on site in mexico city as part of its continued engagement in the country’s digitization of building trades.

the experimental scheme re-imagines candela’s inventive concrete shell structures
image by juan pablo allegre

‘while candela relied on combining hyperbolic paraboloid surfaces (‘hypars’) 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 zaha hadid architects. ‘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 sqm and weighing more than 5 tonnes, was applied on a KnitCrete formwork of only 55 kg.’

the visible inside is an aesthetic surface that displays a colorful pattern
image by philippe block

‘KnitCrete formworks use a custom, 3D-knitted, technical textile as a lightweight, stay-in-place shuttering, coated with a special cement paste to create a rigid mold, and supported by additional falsework elements such as a tensioned cable-net or bending-active splines,’ the design team continues. ‘the hybrid and ultra-lightweight KnitCrete formworks are easily transportable, reduce the need for additional supporting structure and scaffolding, and simplify the logistics on the construction site.’

the interior reveals traces of the supporting cable-net falsework system
image by mariana popescu

the 50 square meters of textile shuttering of KnitCandela’s formwork is comprised of four long strips ranging from 15m to 26m in length. each of the four strips is a seamless, double-layered textile produced as a single piece. two layers of textile fulfill different tasks. the visible inside is an aesthetic surface that displays a colorful pattern and reveals traces of the supporting cable-net falsework system. the exterior surface fulfills technical requirements by including features for inserting, guiding and controlling the position of additional formwork elements.

the project’s dynamic geometry references the colorful traditional dress of jalisco
image by mariana popescu

‘the pockets created between the two layers as part of the spatial knitting process are inflated using standard modeling balloons,’ say the architects. ‘these inflated pockets become cavities in the cast concrete, forming a structurally efficient waffle shell without the need for a complex, wasteful formwork. pockets located on this exterior side of the textile have different knit densities to control the inflated shape and openings for the insertion of the balloons, enabling cavities of different dimensions to be created with one standard balloon size.’

video courtesy of zaha hadid architects

ZHCODE was responsible for the structure’s architectural design
image by lex reiter

the scheme comprises 50 square meters of textile shuttering
image by lex reiter

the formwork is comprised of four long strips ranging from 15m to 26m in length
image courtesy of ZHCODE

each of the four strips is a seamless, double-layered textile produced as a single piece
image by maria verhulst

the ultra-lightweight knitted formwork was carried to mexico from switzerland in a suitcase
image by mariana popescu

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project info:

global dimensions shell: 5.8m x 5.8m x 4.1m
surface area of concrete: 47.5 sqm
weight concrete: 5 tonnes
weight formwork: 30 kg (cable net) + 25 kg (knit)
total length yarn: 350 km
type of yarn: polyester (PES)
total amount of loops: 14,660,028
knitting time: 36 hours
modelling balloons used: 1,000

project team:
block research group, eth zurich (BRG)
zaha hadid computation and design group (ZHCODE)
architecture extrapolated (R-EX)

design:
zaha hadid architects: patrik schumacher, principal
ZHCODE: filippo nassetti, marko margeta, david reeves, shajay bhooshan
BRG: mariana popescu, matthias rippmann, tom van mele, philippe block

KnitCrete technology:
BRG: mariana popescu, tom van mele, philippe block
chair of physical chemistry of building materials, ETH zurich: lex reiter, robert flatt

fabrication and construction:
BRG: mariana popescu, matthias rippmann, alessandro dell’endice, cristian calvo barentin, nora ravanidou
R-EX: horacio bibiano vargas, jose manuel diaz sanchez, asunción zúñiga, agustín lozano álvarez, miguel juárez antonio, filiberto juárez antonio, daniel piña, daniel celin, carlos axel pérez cano, josé luis naranjo olivares, everardo hernández, ramiro tena, alicia nahmad vazquez

structural engineering:
BRG: andrew liew, tom van mele

concrete development:
holcim mexico: jose alfredo rodriguez, carlos eduardo juarez, delia peregrina rizo

site construction coordination:
R-EX: alicia nahmad vazquez

exhibition content, coordination, and curation:
zaha hadid exhibitions and archives: jillian nishi, margaratia valova, daria zolotareva, paz bodelon, elena castaldi, manon janssens, woody yao
ZHCODE: leo bieling, federico borello, filippo nassetti, marko margeta, henry david louth, shajay bhooshan
BRG: mariana popescu, matthias rippmann, noelle paulson, philippe block

sponsors: COMEX, NCCR digital fabrication, ETH zurich, zaha hadid architects, steiger participations SA, holcim mexico, imerys aluminates, boston consulting group
special thanks: grupo altiva, UNAM arquitectura