The true nature of concrete


21026047-abstract-geometric-background-of-the-concrete.jpgSlabs of stone and concrete in the ocean coast landscape. At the start of the 1960s the works of architecture in béton brut inspired by the masterpieces of Le Corbusier and the question of Brutalism are at the center of the international debate, and the work of Louis Isadore Kahn becomes the focus of critics investigating the nature of his concrete.

Henry Russell Hitchcock questions the definition of “Neo-Brutalist” for the Richards Laboratories and the Yale Art Gallery; Jones Causton reveals how Kahn uses columns “ornamented only by the marks left by the wood molds,” in the manner of Auguste Perret; Reyner Banham dubs Kahn, again speaking of the Richards Laboratories, “one of the Brutalists’ favourite architects,” while Vincent J. Scully, Jr., associates Kahn with the “Brutalists” and in particular the “English” ones, discussing the influence of the Maisons Jaoul of Le Corbusier and certain details of the Esherick House, while indicating similarities between the concrete of the Yale Art Gallery and that of Le Corbusier: “The concrete was left rough with the marks of its forms upon it, as Le Corbusier had already treated that material [...].”

When the book The New Brutalism: Ethic or Aesthetic? was published in 1966, where eleven years after his article in “The Architectural Review” Banham takes stock of the main international developments, Kahn’s work – still represented by the Yale Art Gallery alone – is again described against the backdrop of the question regarding the possibility of inserting it, or not, in the “concept of the New Brutalism,” due to its being so “devoted to the ground-rules of academic classicism.” Only the staircase of the Yale Art Gallery seems to possess, in Banham’s view, an expressive force capable of taking béton brut to extreme development:

“The concealment of the stairs within an almost unpierced drum of concrete, heightens one’s awareness of the experience of ascending the stairs, three short flights arranged in a triangle between one floor and the next, rising between sheer walls of concrete, unmodulated by anything beyond the vertically planked shutter-pattern of the concrete, the impress of the fixing studs that held the shuttering together, and the horizontal joint at each floor-level, marking the height of one lift of the shuttering. It is a classic demonstration of absolute Brutalist truth to a particular method of construction, and has the added historical importance of being the most extended demonstration to date, by anyone other than Le Corbusier, of the aesthetics of béton brut."

978-2-940222-77-3.pngBut well prior to the publication of Banham’s essay, Kahn is already making a decisive move beyond the forms of expression of béton brut as it was deployed in the extraordinary sequence of his works extending from the Yale Art Gallery to the First Unitarian Church and School. Starting in the early 1960s, he conducts experimentation on the nature of concrete and the processes of its fabrication, extending to the control of the compound and the system of the formwork itself. Until the end of the 20th century, this was to be the only path capable of progressing beyond the béton brut of Le Corbusier and beyond any New Brutalism, laying the groundwork for an idea of exposed concrete architecture seen as control of the entire construction process. After all, Kahn had proven that he was able to free himself of the aesthetic constraints of béton brut above all with the works in prefabricated concrete and those made with concrete blocks.

One of Kahn’s staff, William S. Huff, who is supervising the worksite of the Tribune Review Building in Greensburg in 1960, recalls a significant anecdote regarding the formwork made with wooden boards used in the United States, and also by Kahn, following the fashion launched by Le Corbusier. “When Corbu made one of his few visits this country, he asked, ‘Why do you people have all those fussy little boards in your concrete work?’ The reply was, ‘Because you do it, master.’ Corbu then said, ‘But you have all that wonderful plywood that comes in great sheets; in Europe we are poor and must use old floor boards, taken up from buildings being demolished, for our formwork.’ Kahn knew the story. He did use floor boards, as Corbu used them, on several of his early buildings – such as the Yale Art Gallery addition. Then, when we did the Salk project, Lou really went all out to employ those large plywood planes in his forms.” 

The process through which Kahn decides to stop using wooden boards and to switch to plywood panels is a bit more complex than Huff would have it. But the value of his story is borne out by the fact that the fundamental passage in Kahn’s way of making formwork takes place precisely in the years of the construction, in 1961-63, of the Carpenter Center for the Visual Arts for Harvard University, in Cambridge, Massachusetts, where Le Corbusier, also thanks to the knowledge of José Luis Sert regarding American techniques and materials for the construction of concrete, uses large plywood panels assembled with V joints. The example of that work, for Kahn, marks the start of a new phase of research on the nature of concrete, which will take him far from the image of béton brut. Though nothing had come of the enlightening criticisms of C. Clark Macomber against Kahn’s preference, on the Yale Art Gallery worksite, for wooden boards, which Macomber saw as a “method of the past.”

At the start of the 1960s, Kahn is involved in the design and construction of the building that marks the crucial chapter in the evolution of his exposed concrete, the Institute of Biology at Torrey Pines, later the Salk Institute for Biological Studies, commissioned in 1959 by Jonas Edward Salk, known for his discovery of a polio vaccine, and built in the state of California, at La Jolla, near San Diego, in the town of Torrey Pines, on a promontory facing the Pacific Ocean – the building is completed in 1965. The design of the imprints on the concrete is not just a direct result of the technical logic of assembly of the formwork, as stated on occasion by Kahn regarding this work. Precisely the most important exposed concrete of the architecture of Kahn bears the secret traces of all the phases of the project, when the surfaces of the Salk Institute are characterized by slabs of stone, as if the face of the concrete onto which the colors and changing light of the ocean weather were crossed by a sequence of layers of textures of different kinds, from those generated by the logics of the worksite to those produced through mnemonic artistic processes. The very nature of the concrete compound and even its color and grain are not immune to Kahn’s initial passion for the stone slabs and the view of the work in the landscape.

Stone face and concrete nucleus: towards a new opus caementicium

Describing the role to be played by concrete in the Salk Institute, to be poured in place, prefabricated and used in blocks to make certain walls, according to the project of 1961, Kahn puts the accent not on the formal qualities of the material, but simply on the potential of the structural capacity of the large beams of the Laboratory Building, precast and equipped with cavities for the physical plant conduits – he writes of “use of concrete in the performance of the hard task of spanning uninterrupted areas.” 

The other two fundamental materials of the Salk Institute, namely glass and stone, are assigned a specific role in viewing, depending on the vantage point of the observer: the glass creates large surfaces for the viewing of landscapes; the stone slabs are placed in the concrete walls to create the color of the envelopes in the landscape. “[...] the use of cut stone, preferably Cordova Shell or Travertine for all enclosing walls and the walls which modify glare,” Kahn writes. The range of essential materials for the architecture of the complex is completed by the various gardens, with their “fresh” air and “waterways.”

It is worth paying attention to the symbolic framework which in Kahn’s outlook should regulate every part of the complex, if we want to fully grasp the meaning attributed to the materials, beyond the technique of their installation. Precisely one of the parts of the Salk Institute most characterized by the envelope of stone slabs set into the concrete core, the Meeting House, a complex of the size of a grand monastery or a palace with a courtyard, is presented by Kahn as a “building which symbolizes the purposes of the Institute.” The plan of the large square hall, at times drawn without the roof, and around which the various other buildings are grouped, is significantly a variation on that of the church in Rochester, with the auditorium surrounded by classrooms. In the differing geometries of those spaces, Kahn stages the metaphor of human beings gathered to spread scientific knowledge. Water and its sounds mark the route that takes the researcher to the Meeting House, from the “square pool,” devised so as to create “a noisy fountain,“ along a “watercourse” as far as the panoramic terrace bordered by a portico, known as the “Colonnaded Ambulatory,” where water springs forth in a “quiet fountain.” Pools of water, terraces for contemplation, slabs of stone with a concrete core are more than clues to Kahn’s passion for the great Roman monumental complexes, like Hadrian’s Villa at Tivoli, which is one of the fundamental points of reference of the Salk Institute, together with the basilica and monastery of San Francesco in Assisi. Precisely as in the Roman wall, where the face and nucleus of opus caementicium constituted an inseparable unit, so Kahn wants to achieve a constructive system with similar characteristics to build his “ruin” on the Pacific coast.

If the stone slabs are introduced for reasons of pictorial image of the Salk Institute in the spectacular coastal landscape, during the course of 1961 Kahn sets out to also give those slabs a fundamental technical role in the fabrication process of the concrete, imagining their use as per

If the stone slabs are introduced for reasons of pictorial image of the Salk Institute in the spectacular coastal landscape, during the course of 1961 Kahn sets out to also give those slabs a fundamental technical role in the fabrication process of the concrete, imagining their use as permanent formwork. The question of stone slabs for the formwork is addressed in June, when members of Kahn’s staff request information from the Texas Limestone Company, based in Austin, to learn if the rectangular stone slabs, measuring 2 x 3 feet, with a thickness of 3 or 4 inches, could form the panels to be left in place on one or both sides of a formwork. They also order samples of the Cordova Shell, to evaluate its “normal range of texture, color and composition.”

In the version of the design of the Meeting House corresponding to this phase of the selection of the materials (many drawings are made in July 1961), Kahn envisions two different systems of construction in reinforced concrete for the walls and the “screen walls.”

The walls are in concrete poured in place, 8 inches thick. While the concrete of the walls inside the Meeting House is poured in wooden formwork, that of the articulated rind of the Meeting House is poured into a formwork system with two different faces: on the external face, the panel is composed of slabs of stone to be left in place; the other face is made with wooden boards. The thickness of these walls with the cladding-formwork incorporated remains at 8 inches (5 of reinforced concrete and 3 of stone). The circular wall of the tower to contain the books – the “Library Stacks” – also has incorporated stone slabs. In these walls, the concrete remains exposed only along the ends of the floor slabs that form horizontal bands in the facades. The other lines would be those of the pattern of joints of the stone slabs.

Kahn envisions another construction system for the “screen walls” that protect the reading and seminar spaces. These “screen walls” are thin shells in prefabricated reinforced concrete, with a thickness of 4 inches. The pillars inserted in the “screen walls” to support the floor slabs of the rooms are also prefabricated. The drawings indicate that in all the prefabricated parts, the concrete is left exposed, free of any imprints of formwork or of joints resulting from the assembly of parts. The concrete of the floor slabs poured in place is also to be left exposed, corresponding to indications written in documents in 1961 and referring to certain parts of the Salk Institute, calling for an “exposed concrete ceiling.” The stone slabs incorporated in the reinforced concrete walls are also found in the construction system for the apartments of the Housing Facilities and the researchers’ quarters connected to the Laboratory Building.

Thick stone rinds, slender screens of prefabricated concrete and concrete walls poured in place would have formed the different visages of the variegated landscape of buildings of the Salk Institute for Biological Studies, in keeping with the project of 1961.

Salk Institute for Biological Studies, La Jolla, California, 1959-65. Meeting House, “Presentation Plan,” 10 July 1961 (LIK, 030.I.C.540.8)

Meeting House, “Library Studies,” 12 July 1961 (LIK, 030.I.C.540.8)
Meeting House, “Wall Sections,” 24 July 1961 (LIK, 030.I.C.540.8)

Extract from Louis I. Kahn - Towards the zero degree of concrete 
By Anna Rosellini 
Published by the Presses polytechniques et universitaires romandes

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