Architectural materials experience reputational changes. A century ago, wood was a cheap and expedient way to build tracts of North American workers’ housing; now, it’s a sustainable solution for ever-larger and taller buildings. Since the beginning of its mass production in the nineteenth century, steel has supported soaring train halls and skyscrapers. Its predecessors, forged iron trusses, were far more ornate than standardized metal members, its character shifting from delicate to muscular.
Then we come to the fallen hero: concrete. Fifty years ago, Canada proudly celebrated its centennial by erecting concrete concert halls, civic plazas and museums from coast to coast. Megastructures built from massive concrete were the future—and with ambitious structures such as Zeidler’s McMaster Health Science Centre and Arcop’s Place Bonaventure, Canada was a global leader.
Now, those same buildings are falling into disrepair, and with them, concrete’s reputation. Concrete is often cast as the villain—synonymous with mean, polluted cities that are gobbling resources and have snuffed out nature.
But if the recent past of concrete looks grey, the future could be green. Last fall, I had the privilege to moderate an architectural round-table at Construct Canada that examined new technologies in concrete. According to the panelists, there may be a time when concrete could again be considered beautiful—and even poetic.
Ronald Rael of California’s Emerging Objects initiated the conversation. Rael’s firm researches the production of strong and inexpensive 3D-printed building components. One recent project, Bloom, is a nine-foot-tall freestanding pavilion composed of 840 customized blocks, 3D-printed from an iron-oxide-free Portland cement polymer. Each brick incorporates part of a structural grid, as well as floral patterned cutouts that allow light to shine into the pavilion’s interior. By using 3D powder printing—rather than the more widespread technology of 3D printing at an architectural scale by extruding wet cement through a nozzle—the finished product is fine-grained and cleanly resolved.
Turning to the East Coast, Brandon Clifford’s work with Matter Design uses 3D-printed moulds to precision-cast concrete into objects that explore the aesthetic of weight and weightlessness. One result is a slender, self-supporting concrete spiral staircase that hangs from the floor above. Another is a large-scale, Easter Island-like sculpture called the McNelly Megalith. Made of foam topped with a one-inch-thick layer of concrete, the 2,000-pound statue can be easily rotated and rocked across a flat surface by a single person, due to a precise calibration of its center of gravity.
On the global scale, architects could have their biggest impact on concrete’s future in China, according to Filippo Gabbiani of Shanghai-based Kokai Studios. From 2011 to 2013, China used more concrete—some 6.6 gigatons—than the United States used in the entire 20th century. Unsurprisingly, many of the speculative buildings produced from that concrete have been of low quality. Much of Kokai’s work focuses on restoring concrete buildings, some of which were built in six months and are in need of renovation four years later. They’ve engaged in programmatic innovation—reinventing a commercial podium as an art institution, for instance—as well as developing new material techniques, such as injected gel compounds that reduce the corrosion of rebar.
Here in Toronto, a concrete legacy is also being reinvented. A week before the roundtable, an announcement was made that the underbelly of a section of the Gardiner Expressway will be renovated into a series of parks and public spaces. Initial renderings by designers Public Work and Ken Greenberg, FRAIC, show a skating rink, public stage and vibrant art installations under the massive concrete supports.
For those walking through the vacant space under the Gardiner, the full majestic potential of its concrete structure is palpable. Our cities have been constructed with concrete—can that concrete continue to sustain the passion of our cites?