Building Mexico: The Many Faces of Mexican Concrete

By Deborah Van Hoewyk

While we can all think of very different examples of Mexican architecture—pyramids, cathedrals, block houses by the roadside–what almost all of it has in common is concrete.  Elsewhere in this issue, you’ll discover that “cement” (calcined lime, clay) is the “glue” that reacts with water to bind aggregates (pebbles, gravel) with sand to make “concrete.”  Cement with sand alone is used to create a smoother mortar for joining blocks. 

Pre-Columbian Concrete—Pyramids and Bridges

Geologically, much of the area of the Aztec and Mayan empires is rife with limestone; in central Mexico, the Aztecs could also use tezontle (a soft, reddish volcanic rock).  Limestone is easily carved with hand tools into large blocks, which then harden on exposure to air.

Limestone blocks weren’t enough, though—ancient builders realized that the blocks should be mortared together with cement, which actually increased the flexibility of large structures, i.e., pyramids.  It is thought that Mayans “discovered” hydraulic (Portland or ferro) cement, which hardens when mixed with water and fillers, from observing the effects of fire on limestone.   At any rate, perhaps as early as 300 BCE, the Mayans had sophisticated kilns to reduce limestone to cement.

Both Mayans and Aztecs then developed a technique that used thinner, mortared block walls filled with cast-in-place concrete, using a coarse limestone aggregate (basically, big gravel).  Using the technique to support arches, the Mayans of Yachilan built a suspension bridge over the Usumacinta River (which separates Chiapas from Guatemala); the bridge, now lost, was the longest in the world until the late 1300s.  Pre-Hispanic builders also thinned out their lime mortar to create a stucco for interior walls, which provided a wonderful surface for hieroglyphics and murals (Tlaxcala, Bonampak).

Something quite remarkable about Mexico’s ancient buildings is that, for the most part, they are impervious to damage from earthquakes. The quakes of September 2017 damaged nearly 2,000 historical structures, 242 of them severely.  The older the structure, however, the less damage—so far, no one has identified a pre-Hispanic structure that has collapsed in an earthquake.

Colonial Concrete—Tension between Old and New

Mexico’s colonial architecture, imported from Spain and designed to impress the “natives” with a vision of European superiority, produced the cathedrals, palaces, and homes we see today in CDMX, Oaxaca, Puebla, Guanajuato, Querétaro, and other colonial cities.  Hidden inside these sometimes very ornate buildings, however, was the work of indigenous masons, who used the traditional cement mortar to join stones and blocks taken from demolished pre-Hispanic sites, as well as the traditional cast-in-place concrete aggregate to fill the interior structures.  Illustrations from Spanish record books of the time, called codices, show the construction of new Christian churches as a collaborative process between indigenous masonry techniques and European applied geometry.

Despite the concrete, these colonial buildings are much more vulnerable to earthquake damage.  (They are also vulnerable, particularly in CDMX, to “differential settling” of buildings sited on ancient lake beds, which magnify earth tremors into rolling waves of instability.)  Stone masonry walls can absorb a surprising amount of tremors and settling; if the mortar cracks, it is easily repaired.  The “great bodily harm” to colonial buildings occurs where the walls meet the European elements.  Analysis of a June 1999 earthquake centered on Tehuacán, which damaged nearly 500 colonial monuments in Oaxaca and Puebla, tells us that the buildings constructed of stone masonry fared the best, but that the European elements (vaults, bell towers, cupolas) tended to crack at the point where they were joined to stone masonry because they couldn’t flex.

Concrete to build “México moderno”

Although other building materials were available in Mexico in the late 19th century, it couldn’t compete with concrete in popularity. In fact, acceptance of concrete at the time reflects a cultural desire to maintain the traditional appearance of Mexico, combined with a fervent marketing effort by the cement industry, which had rediscovered hydraulic cement in the 1880s.  Trade journals emphasized how practical and durable it was as a building material, its decorative potential, how sanitary it was (no vermin, easy to clean), how it would save the forests of central Mexico, and how, with reinforcement, it was resistant to earth tremors.

Mexico’s largest cement producer, Cemex (see elsewhere in this issue) was founded in 1906, and its second largest, Cementos Apasco, was organized in 1928.  Ultimately Cemex cornered the export market, while Apasco (bought by the Swiss conglomerate Holcim in 1964) dominates the internal market for cement products.

When, after the turn of the century, concrete block-making machines arrived, construction with blocks was touted as “modern” and “urban,” appealing to the 6% of Mexico’s population considered wealthy elites. The Mexican Revolution (1910-21) pretty much brought that to a close, but post-revolutionary administrations undertook major building programs, in part to meet increased housing needs as people started moving to urban areas, especially Mexico City.

 

By mid-century, concrete block technology was the major low-cost construction technique, and was recommended for auto-construcción (DIY) house building.  Apasco issued a complete manual in comic-book format, showing exactly how the entire family would participate in building its house.

Cemento Tolteca (now a Cemex subsidiary) also provided a DIY comic book, but felt it necessary to provide domestic instruction on urban living.  The 240-page Manual Tolteca de Autoconstrucción y Mejoramiento de la Vivienda (Tolteca Manual for Self-Construction and Improving Housing) had as its goals: “Mexico should have better self-built houses, and thus better families for a better development of our society.”  Major concerns include having a good place to discard basura, building a good drainage system for the baño, drawing on community support to build each other’s houses, building a separate space for animals (disease! Wash your hands after you touch them! Don’t sleep with them!), providing a place where your children can grow up healthy, strong, and loved.  Many illustrations of septic system and rebar layouts.  Unfortunately, this was 1964, and they recommended corrugated asbestos roofing.

Mid-Century Modern:  Brutalism

The architect called Le Corbusier (he claimed it was from the French for “raven,” but there was a similar name in his family) was born Charles-Édouard Jeanneret-Gris in Switzerland in 1887. Le Corbusier revolutionized modern architecture around the world with béton brut (raw concrete, with the marks of the forms left showing).  The name is unfortunate, as “brutalism” has been used to describe all sorts of buildings that people just plain don’t like that have nothing to do with béton brut, which was intended to reflect the essence of concrete—strength and monumentality. They required careful design and crafting of the formwork to create a surface that expressed both the texture of the concrete and the structural design of the building.  It is often said of “Corbu” that his ability to inspire ideas is just as important as the buildings he himself designed.

And half a dozen or so Mexican architects agreed.  Luis Barragán (1902-88), Juan O’Gorman (1905-82), Mario Pani (1911-93), Augusto H. Álvarez (1914-95), Juan Sordo Magdalena (1916-85), Pedro Ramírez Vázquez (1919-2013), and Teodoro González de León (1926-2016) followed the path of Le Corbusier to define modern Mexican architecture.  Using its characteristic material, concrete, they created an original combination of “international modern” design with, in many cases, pre-Hispanic aesthetics.

Post-Modern Concrete—Architecture as Art

An architect of the same period, Félix Candela (1910-97) took concrete in quite a different direction.  Born in Spain, Candela emigrated to Mexico when he was 26. He reshaped the capabilities of reinforced concrete into thin shells that could carry the curvature of concrete out into space.

Candela’s insight was that reinforced concrete worked superbly in domes or shells; to figure out the engineering, he used hyperbolic paraboloid geometry.  Pringle potato chips are the perfect hyperbolic paraboloids—they don’t crack when piled into the can because the saddle point, where the two “waves” of a Pringle come together, balances the curves to prevent stress fractures from forming.  Eventually, Candela became more interested in the structural engineering of his designs than creating new designs, and became a professor in both Mexico and the U.S.

Candela’s Los Manantiales restaurant in Xochimilco (1958), like pre-Hispanic buildings, survived the devastating 1985 earthquake in fine shape.  The circle of four hyperbolic paraboloids looks like a giant seashell with eight ruffles, floating above the colorful boat-taxis on the canal.  An even more stunning example of Candela’s work was also completed in 1958—Chapel Lomas de Cuernavaca.  The single curve of the chapel reaches far higher than the restaurant, extending architecture into art; nonetheless, everything about the design is structurally necessary.  The concrete shell is about 1½ inches thick on the heights, thickening as it reaches down to the foundation to distribute structural stress.

Candela’s impact has mostly been seen outside Mexico; he inspired several buildings by British-Iraqi superstar architect Zaha Hadid (1950-2106), the first woman to win the Pritzker Architecture Prize. Working with Spanish-born architect and artist Santiago Calatrava (1951 –), Candela reprised the Los Manantiales restaurant for the L’Oceanogràfic, an oceanarium in Valencia, Spain.  In this case, the restaurant itself is in an underwater space encircled with aquaria (opened 2003, after Candela’s death). Calatrava, who said “I deeply consider architecture as an art—the most abstract of all of them,” designed The Oculus (2106), the World Trade Center transit hub in downtown New York City, as well as the stunning Milwaukee Art Museum (2001).

Pushing the Boundaries—Positively Organic Concrete

Frank Lloyd Wright may have coined the term “organic architecture,” but its most striking proponent today is a graduate of and now professor at Mexico’s National School of Architecture at UNAM.  Javier Senosiain (1948 –) is sometimes referred to as a “zoo-” or “bio-morphic” architect, which means the “organic-ness” of his work draws on natural forms for structural inspiration.  (Calatrava’s Oculus has been described as a dove with clipped wings.)

Senosiain started working on low-cost affordable housing while he was still in school, coming up with what he calls a “peanut”—super-light concrete sprayed over a wire frame.  Peanuts can be combined into larger dwellings, or they can be craned into a neighborhood where no dwelling is more than 8 minutes away from a school, shopping, etc.  His best-known project is El Nido de Quetzalcoatl (Quetzalcoatl’s Nest), a 10-condo complex in Naucalpan, north of CDMX (completed 2008).  An aerial view shows what appears to be a fantastic, nest-of-snakes sculpture, with multiple snake’s-head entrances to the condos. Senosiain managed construction so that nearly all the natural features of the site were preserved, and much of the concrete structure is now covered with vegetation.  You can tour Quetzalcoatl’s Nest by prior arrangement: http://organicarchitecture.weebly.com; even better, you and nine of your best friends can stay there, courtesy of Airbnb:  https://www.airbnb.com/rooms/10153978.

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