CONCRETE

It is difficult if not impossible to imagine the 20th century without concrete. Surely the
landscape of modernity and modernization would be unrecognizable without it. By 1900
concrete may indeed have been considered modern, but as pointed out by technical
manuals throughout the century, it was by no means a new material. Ancient builders put
it to use, most notably the Romans, who built walls (faced with brick) and arcuated spans
(the 145-foot span of the Pantheon’s dome the most famous and well-preserved
example). This classical pedigree appealed to many architects of the early 20th century,
although modern concrete practice had more recent origins. Europeans experimented
with it in the 18th century, when the English engineer John Smeaton used a form of
hydraulic cement (a cement that hardens underwater) to rebuild the wall and lighthouse at
Eddy-stone off the Cornwall coast in 1756. The French began their own experiments
some 30 years later, using a combination of clay and cement from limestone. Louis Vicat
perfected hydraulic cement around 1800, and by 1850 Joseph Monier was producing
concrete flowerpots and sewer pipes using wire mesh and timber molds. In 1824 the
English bricklayer John Aspdin invented a type of cement dubbed “Portland,” after the
stone it resembled. This high-strength variety proved crucial, for it became, and remains,
Entries A–F 551
the standard binding agent in the concrete used today. Portland cement was exported to
the United States at the end of the American Civil War, and as in much of Europe,
concrete frame structures were constructed for a variety of industrial uses. Particularly
valuable for fireproof attributes, concrete effectively insulated the iron or steel embedded
within. In some places, such as the American northeast, they were a relatively common
sight by the start of the 20th century. By 1887 the French engineer and building
entrepreneur François Hennebique patented a host of techniques for embedding steel bars
in concrete.
How best to utilize concrete and how to appreciate and interpret its
cultural meaning remained one of the more interesting and politically
volatile architectural debates of the century. This ongoing state of flux
involved more than technical development. By the end of World War II
engineers, architects, builders, and others helped develop concrete as a
common building material across the globe. From great hope to corporate
or state-induced eyesore, perhaps no other material would be perceived in
so many contrasting ways during the 20th century. One of several
materials embraced by avant-garde architects for its revolutionary
prospects, critics would come to vilify the material, associating it with the
oppressive characteristics of modern power structures. Through it all the
material maintained a pragmatic usefulness.
Technical Aspects
Concrete is a composite material produced by mixing a paste of cement and water with
inert materials called aggregates. Because concrete is mixed and poured, it is well suited
for molds and can be molded around reinforcing steel, a practice so common that by 1900
nearly all concrete structures were reinforced in some way by steel hidden from view.
The first ingredient, cement paste, is the binding agent, and a number of different types
were developed throughout the century. Consisting of Portland cement and water, this
paste hardens via a curing process called hydration. The second ingredient, aggregates,
varies considerably in size from sand particles to 3-inch rocks mixed with the paste.
Lightweight varieties of concrete substitute these aggregates for expanded shale, slate, or
slag to reduce the finished product’s weight. Because concrete’s usefulness is
complicated by its own dead load, a variety of engineers and builders have sought
inventive alternatives. One of the more unusual experiments was conducted by the
American architect Bernard May-beck (1923), who sought a low-cost remedy for the
housing shortage after a fire devastated a portion of Berkeley, California. In a clotheswashing
drum he combined cement paste, water, and sand; added some chemicals; and
after mixing the concoction he dipped burlap sacks into the tank and pasted them onto
wooden wall studs to form a concrete cladding. Calling this technique Bubble Stone for
Encyclopedia of 20th-century architecture 552
its unique appearance, Maybeck boasted that home owners could use it themselves
because an average man could lift a hay-bale-sized chunk of this “stone” above his head.
Well-made concrete enjoys significant resistance to compression, but unlike steel it
has little strength against tensile stress. The compressive strength of concrete is primarily
based on the ratio of water to cement. Experiments both in the field and in laboratories
led engineers in an ongoing effort to increase the material’s strength and decrease curing
time. Generally speaking, the smaller the ratio of water to cement paste (i.e., the less
water compared to cement paste), the stronger the concrete.
Once mixed, concrete is poured into molds called formwork, which may vary from a
hole dug out of the earth for a foundation, to wood boards bolted together, to fiberglass
panels. In some cases an entire substructure of forms must be constructed, itself a selfsupporting
structure requiring careful design and inspection by engineers and contractors.
In order to ensure a more controlled mixing process, concrete elements are often poured
in a factory or in a semiremote location on the building site set aside for the purpose. The
pour is crucial because laborers must work the paste and aggregates evenly throughout
the formwork so that they do not shift prelaid rebar out of its intended positions. Pipes
and conduits that must pass through the finished concrete must be set into position prior
to the pour as well and remain undisturbed by laborers’ efforts to fill the forms. As the
mix is spread within the formwork, laborers must ensure that all voids are filled and that
the aggregate is evenly distributed. The more fluid the mix, that is, the greater the ratio of
water to cement paste, the more workable the pour. Increasing the water makes for easier
construction, but weakens compressive strength. In colder climates air-entraining agents
are often added to increase workability and resistance to the heaving resulting from water
turning to ice.
Concrete must be mixed for a sustained period of time, so that the finished product
exhibits the properties of strength and durability designed by engineers. The development
and widespread marketing of gasoline-powered automobiles and trucks have had an
influence in the mixing process, especially in the United States. The truck was both a
prerequisite and a consequence of the parallel development of concrete construction.
Improvements in road construction, a development that was facilitated by the concrete
industry, in turn facilitated the widespread acceptance of the automobile. Likewise, the
cement-mixing gasoline-powered truck is ideally suited to concrete construction because
while en route from the factory the truck mixes the cement paste, water, and aggregates
in a revolving drum. Once poured and left to remain still, concrete sets in up to three
days, then cures for usually one month, depending on the type of ingredients in the
mixture and the climatic conditions at the site or factory. After engineers determine the
concrete is strong enough to support its own weight, laborers remove the formwork for
reuse at the next pour. In cold conditions curing concrete must be covered to ensure the
temperature necessary for developing a designed compressive strength. Curing is a
chemical process (not a process of desiccation) in which water reacts with the cement
paste and generates heat. Although hydration can occur even when concrete is
underwater, even well-made concrete is not completely watertight. Over time exposed
surfaces tend to absorb water that can pass into interior space. Other liabilities were
discovered throughout the century, such as the material’s poor insulating properties and
the particularly dangerous problem called creep. Horizontal concrete structural members
(slabs and beams) develop the tendency to gradually deflect over long periods of time,
Entries A–F 553
and this can become so severe as to make buildings uninhabitable. Structural engineers
devised prestressing strategies to counter this creeping deflection.
Properties of strength and workability have not monopolized
experimentation. Designers and builders have devised myriad ways of
altering the construction process to obtain specific aesthetic effects.
Various admixtures, especially those added at the end of a pour, have been
used to alter the color of the finished material. Paolo Soleri experimented
with using mounds of sand as a formwork in building concrete shells and
half domes in the Arizona desert, even using the red and yellow color of
the local sand and clay as part of the cement paste and aggregate mixture
(Arcosanti, c.1970). These colors were transferred to the finished product.
The subtractive volume of the formwork, and even the texture of its
interior surfaces, has absorbed the attention of architects interested in
manipulating the texture and the quality of concrete’s finished surface.
Ornamental aggregates have been left exposed to give concrete a more
rustic appearance, and a variety of surface treatments have been developed
to alter the appearance of the finished concrete. The 1960s and 1970s in
particular was a period in which concrete surfaces were used as a finish on
a massive and widespread basis. Paul Rudolph’s Art and Architecture
Building at Yale University (1964) was a grand experiment in finish
treatment, where the architect and contractor devised a method of using
grooved forms that left corresponding vertical fins that ran the full sevenstory
height of the building’s towers. Workmen removed the forms and
then with hammer and chisel knocked away a portion of the fins to create
a rusticated and jagged finish. The resulting grooves channeled rainwater
down the facade in a controlled manner, which in turn limited the effect of
stains on the finished surface, and at a distance the rough texture of the
towers blended into the neo-Gothic architectural context of the
neighborhood.
Stylistic Issues
By 1920 concrete helped inspire architects to visualize massively scaled cities, and for
the next 40 years they sought to refashion the urban landscape in a wholly new and
modern reconfiguration of the 19th-century city. With the turning over of the colonial
order following World War II, much of the world embraced concrete and its promise, but
by the last quarter of the century, the material’s own success wrought a searing critique
Encyclopedia of 20th-century architecture 554
against its aesthetic properties and monolithic application. Finally, in the hands of a few
architects across the globe, concrete once again continued as a material with striking
aesthetic possibilities at the close of the century.
The fact that steel-reinforced concrete structures were already fairly common by the
start of the 20th century, at least in parts of Western Europe and North America, is
attested to by the number of notable works designed and constructed between 1900 and
1910. Thomas Edison was already promoting his “monolithic houses” by that time, Frank
Lloyd Wright had designed Unity Temple (Oak Park, 1906), Antoni Gaudí had begun
construction on his Casa Milá apartment block (Barcelona, 1905), and Auguste Perret had
completed the apartment house at 25 bis, rue Franklin (Paris, 1903), followed by a
concrete-frame garage (Paris, 1905). Although concrete had already been employed for
some 30 years as an industrial building material, by the turn of the century it was still too
new to be associated with industrialism. That distinction belonged to iron and steel, the
constituent elements of a landscape troubled by smokestacks and locomotives. Many
architects and engineers also looked to concrete as an alternative to stone, perhaps
because of the many similarities between the two materials. The weight of stone tended
to be a prime factor as a building material, requiring extensive formwork during
construction. Concrete was perceived as the thinking man’s building material, requiring a
scientific mind to fully exploit its properties, which helped rehabilitate its status as a
rough and crude version of stone. Mixtures and ratios, after all, required experimentation
and theorizing by engineers who took out patents on their ideas. The possibility of
creating a monolithic structure excited architects who understood that with concrete each
element (walls, columns, floor, and roof) would resist loads as one integrated structure.
This was an important and tantalizing potential, because for many architects in the early
20th century, the key problem of the day was finding a way to bring pragmatic
considerations of the engineer together with the architect’s taste for beauty and formal
unity.
The French architect Perret is generally looked to as the first 20th-century architect to
fuse the new medium of concrete with existing attempts to find a modern and modernized
expression of architecture. Greatly influenced by the ideas of Viollet-le-Duc, Abbé
Laugier, and especially his mentor Julien Guadet, he sought to extend and embrace
classical ideas about proportions and order to the technology of the 20th century. He saw
concrete as an ideal medium for creating frame structures, articulating columns in a clear
and rational expression of their structural use, rather than clothing and thus obscuring
them in cladding. To emphasize the trabeated character of the structural frame at the
apartment building at 25 bis, rue Franklin, Perret designed the street-facing fenestration
as large as local ordinances allowed. The structure was not clearly articulated; however,
Perret used a subtle technique of varying color and texture to distinguish what was load
bearing from what was not. By varying the color and texture of the facade panels and by
recessing windows and cantilevering the second floor beyond the ground floor ever so
slightly, Perret deemphasized the mass-wall characteristics of the concrete. The effort to
read the facade like a frame-and-panel assemblage, a more truthful reading of the
structure, was Perret’s way of maintaining continuity with the neorational ideas of the
past.
The engineer, builder, and pioneer in concrete construction, François Hennebique,
acted as consultant on Perret’s project. Hennebique had several patents for concrete
Entries A–F 555
members already, and unlike the architect who strove for a homogeneous and uniform
structural expression, Hennebique articulated the joints between column and beam by
thickening the columns and extending the beams in a cantilevered bracket (Hennebique
House, Paris, 1904). Engineers such as Robert Maillart and Eugene Freyssinet, however,
were the first to appreciate concrete’s nonrectilinear potential. Maillart designed arcuated
bridges whereas Freyssinet built factories with curvilinear concrete-shell roofs, and
perhaps their lack of concern over spatial enclosure allowed them the freedom to
experiment more easily with form and thus more fully capitalize on the unique prospects
of the material. Late 19th-century experiments with concrete reinforced by wire mesh
produced curvilinear ship hulls that prefigured this later engineering development. Perret
by necessity had to think in terms of both space and structure, and influenced by the
architectural concerns of his day, he was less willing to depart from the rectilinear norm
that marked architectural design at the turn of the century. Although concrete may have
seemed an alternative to the industrial steel aesthetic, ironically architects increasingly
saw in the material an opportunity to use it as a medium for expressing the machine age.
For many repetition of the rectilinear module was the key. Le Corbusier’s influential
post-World War I solution to the housing shortage in Flanders was the Domino housing
project. Six concrete columns, three horizontal slabs, foundation blocks, and switchback
stairs comprised the fundamental elements of this kit of parts, and the articulation
between column and slab was without beams, the trabeation fully embedded and
embodied in the clean and ornament-free lines of the steel-reinforced concrete. Le
Corbusier asserted this system was an economical solution that could be mass-produced,
with wall elements added to complete this housing scheme. Although this model had little
practical application during and immediately after the war, it was nonetheless a powerful
inspiration among architectural thinkers who sought a fit between modern materials and
modern architectural aesthetics. As an idealized shelter, stripped of non-load-bearing
elements and reduced to the purity of column and horizontal planar members, it was
hailed as a bold gesture toward a new symbolic architectural representation free of
historical iconography.
Thirty years later Le Corbusier was busy designing an entire city (Chandigarh, India)
out of concrete and masonry, but in 1946 he remarked on an important transformation of
thought that had taken place. From a “machine infatuation” to a more “spiritual” pursuit
of the material’s potential, he claimed that architects now sought to tease out less sterile
formal aspects of concrete. The small music pavilion for the Phillips Company at the
1958 World Exposition in Brussels reveals how concrete could be thought of as more
than a respite from historical reference. As a technologically sophisticated building
material ripe with technical problems, it was deemed ideal for creating a space that
celebrated a marriage between multiple and technologically sophisticated art forms. The
project architect, Iannis Xenakis, designed the general layout, leaving Le Corbusier to
concentrate on finding formal expression to match the “electronic poem” composed by
Edgard Varèse, the multimedia piece that combined visual projection with electronic
sound. The architects devised a hyperbolic paraboloid shell to enclose the exhibition
space, believing that using concrete here would be economical because this complex
form could be created with straight lines and repetitive rectilinear sections. The shells of
the paraboloid needed to be thin—too thin, in fact, to cast in place—so the architects
sought the expertise of engineers in devising a system of prestressed panels formed on
Encyclopedia of 20th-century architecture 556
sand in a nearby warehouse, then bolted together and stiffened by longitudinal precast
ribs.
The Phillips Pavilion, however, was an exception. For the most part, concrete had
supplanted stone as the building material of weight and dignity. Although engineers
occasionally utilized its fluid-form properties to advantage (see especially the most
famous case, the Chapel Notre-Dame-du-Haut by Le Corbusier), architects typically
bowed to the thrift of rectilinearity. Concrete remained a conservative but increasingly
popular building material. Louis Kahn’s Salk Institute (1959–65) is perhaps the best
example illustrating how an architect could use the modernist idiom to create dignified
space. The blank gray laboratory facades alternating with fenestration and the mass of
concrete stair towers created a serene yet monumental outdoor court. Kahn christened
this space “sublime,” a term repeated by critics at a loss to surpass the analysis of the
designer. The spiritual quality of this central but little-used space was the result of the
architect’s effort to bring together in an artistic treatment two disciplines that seemed to
be yawning further apart in the 20th century. Again, architecture was to marry the
rationalism of science to the romanticism of art, a marriage many architectural thinkers
believed was more important than ever after World War II and the advent of what many
thought was the ultimate work of science, the atomic bomb. It was, in fact, the technical
demands of materials like concrete that led architects like Pier Luigi Nervi, a pioneer in
the use of concrete himself, to insist that “architecture is and must be a synthesis of
technology and art,” rather than “separate aspects” of a building process. The architect’s
role was changing—no longer an agent of technological change, but a mediator of
technology. Nervi gave a series of lectures at Harvard University in the early 1960s
urging students and practitioners to embrace a disciplinary unity, a sentiment that belied
anxieties over the architect’s weakening influence. The technical demands of concrete
forced engineers to specialize in its design and maintenance, a task few architects were
capable of handling competently.
Although a naïve booster of a synthesized design process, Nervi was at least prescient
about one aspect of concrete’s future. In those same lectures he predicted that concrete
would be utilized as the principal building material in ever-larger public and commercial
projects. Across the globe governments and government agencies, as well as wealthy
groups of profit-interested private companies, had already been forcing dramatic
interventions in the landscape. Urban renewal and new towns, often composed of largescale
multiblock buildings, housing blocks, hotels, convention centers, and government
administration centers, came to dominate wherever they were built. Modernist vocabulary
did not change by this embrace of the large and the hard as much as it grew in scale. The
Brutalism movement grew out of this application of concrete and masonry, and the
multilane freeway elevated on giant-sized piers designed entirely by civil and structural
engineers came to mark the American urban landscape in particular. Even before Nervi
finished his lectures, a skepticism of this progressive gigantism gained momentum,
particularly with such books as Jane Jacobs’s The Death and Life of the Great American City (1964). She fronted a chorus
questioning the inhumane character that resulted in part from gross-scaled concrete
construction. Although but one of many building materials put to use in this boom,
concrete had finally supplanted steel as the epitome of modernity’s failings. Archi tects
who achieved fame via an expertise in the design of the monolithic concrete environment
watched as their careers withered into obscurity (see especially Paul Rudolph).
Entries A–F 557
The rise of critical regionalism as a critique of modernism, and especially the
development of Postmodern architecture, has meant a shift away from the monolithic at
many scales. The large-scale concrete block has given way in architectural importance to
smaller works that have been built in a whole range of locales across the world. Even
large-scale building complexes have been commissioned in smaller pieces to a handful of
architects. By the end of the 20th century, however, concrete continued to offer a small
number of architects the possibilities of abstract design in a medium affording a range of
formal possibilities limited not so much by physics as by budgets.
Although concrete remained a vital structural material, as an aesthetic
medium it was perceived as a stylistically austere means of creating
minimalist space but only at great expense. Architects such as Enrique
Norton of Mexico City and Tadao Ando of Osaka relied on many
techniques from the modernist boom, using concrete as a decorative as
well as spatial and structural medium. They went to the trouble of
designing the formwork themselves to create a grid of indentations
punctuated by bolt holes left over from the forms during curing. In House
Le by Norton (Mexico City, 1995), the three-story concrete facade was
articulated with this pattern in a way that softened the otherwise massive
plane while maintaining an expression of urban privacy that embodies the
heart of this compact courtyard house. Ando’s austere but elegant Church
of the Light (Osaka, 1989) used a similar texture derived from impressions
left by the formwork. In this case the partitioning of the concrete walls by
the grid of form lines gave the finished surface a taut effect, one that
makes the mass wall seem more like a tensile surface. The small size of
the church, coupled with the application of simple but stark openings
articulating one space from the next, meant that as the principal finish
material, the concrete was not overwhelming or oppressive.
Political and Economic Influences
Concrete persistently teased architects with the allure of its fluid form and sculptural
potential. Steel-reinforced concrete has indeed been designed and constructed as
curvilinear elements, but such practice proved expensive because forms typically had to
be customized and could not be used repetitively. Using concrete as a finish material
meant ensuring a smooth and visually clean and stainless appearance. This required
increased care, skill, and on-site inspection, which translated into higher budgets. It is
perhaps ironic that at the end of the century, when curvilinear forms had become an
obsession for many architects in a wide variety of materials, concrete had become
associated with a rectilinearity that Perret would have appreciated 100 years earlier. The
Encyclopedia of 20th-century architecture 558
Stone Cloud House by Kyu Sung Woo (Seoul, 1996) reveals the pragmatic uses concrete
was often put to at the end of the century. The villa encloses a courtyard that spatially
unites the extended family, each unit of the family dwelling in spaces enclosed by castin-
place concrete bearing walls, but finished with stone from a local quarry. The stone is
arranged in a pattern of square-panel courses that echo the stone flooring as well as the
rectilinearity of the various spatial units that enclose the court-yard. The pattern is also
vaguely reflective of the concrete it hides and adorns.
The success of concrete as a building material early in the century stemmed in large
part from the argument by builders, engineers, and architects that concrete was cheaper
than timber and stone. This was true only because the majority of labor required in
creating concrete structures demanded less skill and training than stonemasonry.
Concrete construction demanded a shift in thinking, a shift that had profound
consequences in the construction industry at large. At the turn of the century those few
architects, engineers, and contractors who insisted on the application of steel-reinforced
concrete strove to bring science into a practice dominated by a craft tradition. In their
view the demands of concrete construction meant that technical innovation would prevail
over what was perceived as the monopoly of an artisan class.
Unlike stone construction, a monumental material that concrete ultimately came to
supplant in many respects, concrete requires a small group of highly skilled technicians to
ensure a proper and safe construction process. This stratification of labor between the
skilled engineers and foremen, and the unskilled and in some cases untrained laborers,
proved to be an important and distinctive aspect of the modernization of the building
industry as a whole and became typical of virtually every modernizing industry.
Demanding empirical testing both in the laboratory and in the field, as well as inspections
that only well-educated and trained engineers were capable of, this new organization
effectively diminished the power of older family and regionalbased trade networks. These
older craft unions, as historian Amy Slaton has argued, the bricklayers and the
stonecutters in particular, “had little influence in the concrete industry, and technological
advance helped render their diminished role both possible and permanent” (2000).
The success of this managerial transformation has been amply demonstrated by the
widespread synthesis of the concrete construction industry across the globe, particularly
in the post-World War II period, and its effect on other construction trades. Steelreinforced
concrete structures, many resembling in skeletal form Le Corbusier’s Dom-ino
house, have appeared in regions where unskilled labor is plentiful. The limiting factor in
such construction tended to be set by the cost of reinforcing steel rather than the technical
expertise of the engineering profession in the newly liberated nations, many of which
realized an acute need for large-scale buildings to house new political, financial, and
domestic populations. Many governments, particularly in the Soviet Union, as well as
myriad newly independent nations after the war, built large-scale projects in concrete to
house the populace. Urban renewal in the United States and postwar reconstruction
largely funded by the Marshall Plan vaulted concrete into a position as the preeminent
building material during the 1950s and 1960s and even later. In some regard the
modernist effort to make architecture relevant to social and economic problems, an effort
epitomized by massively scaled visions of new cities such as Le Corbusier’s plans to
remake Paris, came as near realization during this period as it ever would. Although
concrete was by no means the only material put to use in these grand visions, by the
Entries A–F 559
1970s it was a material that not only seemed to epitomize modernity and modernization
both materially and politically, it had become inextricably associated with the problems
of excess and scale in both socialist and capitalist planning.