Cement Age / Concrete Nation
Kleinman Forum, Fisher Fine Arts Library, 220 South 34th Street, Philadelphia PA
Stuart Weitzman School of Design
102 Meyerson Hall
210 South 34th Street
Philadelphia, PA 19104
Kleinman Forum, Fisher Fine Arts Library, 220 South 34th Street, Philadelphia PA
200 years have now passed since the introduction of artificial Portland cement in 1824. No other building material since the Industrial Revolution has so transformed the built environment, ushering in the modern age. As the main ingredient in concrete, cement is the most widely used substance on Earth after water. It is also recognized as the third largest carbon dioxide emitter in the world.
The technology and use of concrete in engineering and architecture have evolved greatly from its introduction in the 3rd century BCE by Roman engineers to its reemergence in the 19th century and prominence as the signature material of modern architecture and the development of 20th century cities. With over a century of building, modern concrete ‘heritage’ is now a critical topic of interest for design and preservation professionals alike.
Cement Age/Concrete Nation will offer an in-depth study of the origins of modern concrete heritage, its conservation issues and methods, and current demands for sustainability and ecological transition. Philadelphia, by virtue of its rich collection of concrete architecture by influential architects and engineers spanning the 20th century, and its proximity to the Lehigh Valley, birthplace of American artificial cement in 1871, provides a unique setting for the celebration of this milestone in building technology.
The conference will be relevant to those interested in technical and construction history, 19th and 20th century architecture and engineering, and the conservation of concrete and related cementitious construction materials.
Histories of modern concrete use have rested largely on two features of the material, both deriving from its fluid nature: its relatively inexpensive character for large- scale application compared to older “batch” methods such as masonry or carpentry; and its suitability for expressing elaborate aesthetic intentions. While these narratives have helped us see the profoundly interconnected nature of materiality and design in the history of building, a deeply consequential pattern of social relations might also be exposed by historicizing this familiar material: a set of conditions associated with capitalism and its labor systems that have undergirded both the commercial and aesthetic appeal of concrete construction in the United States.
Through a critical history of commercial cement and concrete use, we can probe prevailing conceptions of efficient and affordable building processes and how these determinations have supported capital investment. The priority long given by building firms and owners to cost savings, in other words, frames the historical question, not the answer to our investigations of concrete’s unceasing popularity. We can find in the 20th-century expansion of concrete use in the US a powerful record of industrial labor relations, including ideas of fair occupational opportunities, reliable technical knowledge, and the origins of both in racial and gender ideologies. By bringing out the role of majority interests in the wide take-up of concrete, we confront the embeddedness of architecture in timelines of wealth and social influence and engage with the inescapable problem of how as historians we can most fully account for our built and social environments.
With the naked eye, it's hard to see how a drab gray powder has made such an impact on modern society. Yet, under the microscope, portland cement is shown to be a carefully engineered artificial rock made to suit an ever-growing number of structural, functional, and aesthetic purposes. While we celebrate the anniversary of Aspdin's invention, it is important to recognize that portland cement development was as much evolution as revolution. From the mid-eighteenth century, discoveries of rocks that naturally produce hydraulic binders when calcined instigated a search for an artificial cement recipe better suited to industrial process. Improvements in that recipe continue to be made today.
Viewing portland cement under the microscope allows us to track the evolution of the product and observe how designers have made best use of its properties. At its earliest in the United States, engineers imported British cement to create artificial stone that could not be made successfully with any other American product. Once made in the United States, innovative designers such as Rafael Gaustavino could adapt the now inexpensive and reliable product to the creation of sound-absorbing tiles for his soaring vaults and domes. A small modification of the cement chemistry provided the industry with a non-staining product for marble and limestone masonry of any scale. Major infrastructural projects of the twentieth century benefited from the Abrams water-cement ratio law and early belite-rich cements that were volume stable. Further benefit to infrastructure relied on the addition of supplementary cementitious materials that react with portland cement hydrates to yield a more chemically stable and water-resistant matrix.
Schokbeton was a company and patented system of Dutch origin for prefabricating reinforced concrete building components. Originally patented in 1934, Schokbeton was hugely successful, as evidenced by its export, licensing, and franchising around the globe. The essence of the Schokbeton patent was lifting and dropping the mould at a high frequency while pouring the concrete (with a low water-cement-factor), instantly compacting the concrete, resulting in very dense concrete, hardly permeable for water and oxygen.
Concrete precasting was a response to a variety of economic, environmental, and social forces working against in-situ concrete construction. After the turn of the twentieth century, ever-increasing labor costs made in-situ construction economically uncompetitive, particularly for architectural-quality concrete. In response, precasting introduced systematized concrete production in a weather-protected plant for more efficient production, manageable construction schedules, consistency, and elevated quality than site construction could achieve.
Schokbeton arrived in the US with the first mainland franchise in 1960 to a newly formed company, Eastern Schokbeton. Eventually, Schokbeton was licensed and franchised nationwide in the US and produced architectural precast concrete for many prominent American mid-century architects.
The intrinsic durability of the material, the high quality of engineering and technical design within the company as well as the cooperation with renowned architects allow for a retrospective analysis of the architectural legacy and impact of Schokbeton.
This duo-presentation will trace Schokbeton’s interesting post-war path from the Netherlands to the USA and its distribution of franchisees and licensees across the USA. It will show many buildings, dive into concrete recipes and refer to archival material to elaborate on the introduction, growth, maturity and decline of Schokbeton. By doing so it will explore how precasting changed concrete architecture was designed and constructed.
Reinforced concrete was an integral part of the construction and development of the Pacific Northwest in the 20th century. In the 1920s, concrete ‘skyscrapers’ remade a downtown core. During the Great Depression and WWII, concrete box girder bridges became so lightweight they began to float. In the post-war period, geometrically precise formwork led to unparalleled thinness and efficiency in thin-shell concrete construction.
In the early 1950s, the architectural engineer Jack Christiansen emerged as a significant designer of thin-shell structures, bringing a logic of construction and economic efficiency to the architecturally expressive medium. Because of this approach Christiansen was able to design hundreds of cost-effective, thin-shell structures in the Northwest and beyond, joining a global cohort of thin-shell designers like Felix Candela and Heinz Isler as one of the most prolific in the world. His design work culminated in the Seattle Kingdome (1976-2000) – the largest, free-standing concrete dome in the world in its time.
Christiansen’s design career provides insight into the particularities of thin shells of reinforced concrete, revealing their latent capabilities and potentials as well as their shortcomings. The range of structural forms and architectural uses speak to their strength and versatility. However, building performance concerns of waterproofing, insulation and acoustical treatment often complicated their future success.
In the Spanish Caribbean (Cuba, Puerto Rico, and the Dominican Republic), imported materials and construction techniques helped produce buildings that were fire, water, and vermin-proof, during the first decades of the 20th century. Prefabrication, standardization, manufacturing speed and installation, as well as innovative means and methods, revolutionized the construction industry of the region. Often earlier than in the United States, and almost immediately adopted, was imported “Portland” cement. As one of the most innovative materials of the 19th century, cement in barrels as well as prefabricated ornamental floor tiles were imported, embraced, and used in these island-countries since the late 1900s. Cement was used to produce blocks or artificial stone, cast-stone, ornamental floor tiles, reinforced concrete, and many other molded cladding materials used as covering for steel-framed structures. The use of cement (quick-setting due to the high humidity of the local tropical climate) produced long-lasting individual components and buildings that would survive indefinitely in these territories affected by high marine salinity, earthquakes and hurricanes.
Regional cement factories were established as early as 1895 in Cuba, facilitating faster fabrication methods, since the lighter new buildings were constructed with the use of repetitive processes facilitated using reusable molds. This mostly early 20th century molded architecture, with an infinite series of combinable elements such as columns, balconies, ornament, as well as roofs and walls made with Portland cement, quickly filled neighborhoods in Cuban, Puerto Rican and Dominican environs. Catalogs produced in each of these countries included innovative prefabricated cement architectural elements, which would maintain the essence of local traditional architecture translated into cement and reinforced concrete. The new cataloged “cement architectural kit of parts” would help evolve original designs, while maintaining popular layouts with the front balcony as a recurring and important architectural element for cultural communication.
The Brion Memorial (1969-78) by Carlo Scarpa (1906-1978) is an exceptional study case because of its monumental character, combined with the author's desire to imagine its ageing, (not its damage) over time. The almost exclusive use of reinforced concrete for the built architecture and the choice of experimental technical solutions place this architectural complex within the field of contemporary architecture preservation, due to the theoretical and operational difficulties in defining the intervention. Furthermore, the preservation problems of exposed concrete characterised by peculiar formal values, are well known. Actually, Scarpa's concrete processing techniques provide a wide range of surfaces and related forms of degradation, which require specific approaches to their preservation.
An original and complex system of surveying and interpreting the construction elements is applied, also proposing a specific rendering methodology - graphic, photographic and descriptive -in order to represent both technological characteristics and degradation phenomena, as well as operative indications such as diagnostic investigations or preservation and maintenance interventions.
This knowledge path led to the definition of the necessary interventions: the outcome of the investigation phase allowed the interventions to be tested on a portion of the artefact (2018); once validated, it was extended to the entire complex. The restoration of the Brion Memorial provided an extraordinary opportunity to reflect on the methods and limits of preservation interventions and to update the current state of the art in terms of technical solutions. The restoration was completed in 2020.
One hundred and eight years ago, architectural sculptor John J. Earley unveiled the potential for exposed aggregate concrete as an architectural finish material. Over the next three decades, he established not just a single architectural finish, but a family of techniques to create a vast range of forms, colors and textures with concrete. In their total effect, John J. Earley’s innovations breathed life and spirit into concrete as a modern architectural material.
Earley’s greatest project was the stunning Baha’i House of Worship in Wilmette, Illinois. The Temple’s design presented Earley with both an opportunity and a set of new challenges that required ingenious technical developments. In 1933, for the Temple’s dome, Earley Studio created some of the first architectural precast concrete panels installed on a structural steel framework. For seventeen more years, the Studio produced ornamentation for the Temple’s exquisitely beautiful, architectural finishes.
When areas of the Baha’i Temple needed restoration, no similar repairs of exposed aggregate concrete had been done. The team not only had to identify the problems’ causes and design solutions, it had to rediscover John J. Earley’s process and adapt his historical methods to the requirements of modern material science. Restoration projects between 1987 and 2010 required extensive research, testing and experimentation to create repairs that match John J. Earley’s original work.
This presentation will survey John J. Earley’s key projects and technical innovations, dive into Earley Studio’s construction of the Baha’i Temple’s cladding, and share methods developed for restoration of extraordinary architectural concrete.
Completed in 1908 and featured on the cover of Frank Lloyd Wright’s Wasmuth Portfolio, Unity Temple changed the course of architecture. While not the first building made solely of cast in place concrete it was an early use of the material and forcefully demonstrated the power and possibilities of this modern material. Being an early example of concrete being used in this way, its long-term behavior was poorly understood. As a result, by the 1970s the building exhibited significant deterioration. A repair program prepared by removing approximately an inch of the existing concrete surfaces and applying “shotcrete” to protect the underlying structure. This stemmed the tide of deterioration for some time, but by the late 1990s the overhangs were in a deplorable state and needed major repairs. That work was completed by removing and recasting the overhangs and applying shotcrete to the underside. While these repairs addressed the most pressing problems, the rest of the building was in dire need of attention. The Unity Temple Restoration Master Plan was completed in 2006 and finally in fall of 2014 funding was in place and the planning began for complete $25M restoration of the building.
The restoration included addressing the entire concrete façade. The work in the 1970s and been done in a manner that made matching the existing surfaces extraordinarily challenging. Months of planning and mockup trials were needed to establish an acceptable methodology and matching protocol for the work. Once that was completed, the work proceeded in an orderly manner with only a few instances of problems that were eventually resolved. The result was a return of Unity Temple to its stunning presence on Lake Street in Oak Park. The building is now one of eight Frank Lloyd Wright sites listed at World Heritage.
The presentation will describe the restoration process in detail and will be made by the architect and specialty contracting team who executed the work.
The 1962 Seattle World’s Fair was a global exposition of technological ambition in the Space Age. The US Science Pavilion at the fair, designed by the architect Minoru Yamasaki and structural engineer Jack Christiansen, pushed the technological and practical boundaries of pre-stressed concrete to create a light, expressive and durable Pavilion complex. Aligned with the mission of the Pavilion to promote scientific advancements, the pre-stressed concrete itself was celebrated a legitimate “material of the future”.
The US Science Pavilion consisted of five, low-rise rectangular buildings grouped around a central courtyard. Each building was made of ribbed, precast concrete bearing walls that supported long-span prestressed concrete T-beams. Intricately patterned and faced with crushed quartz, the panel walls were pure white and glistened in the sun. The courtyard was marked by a series of post-tensioned elevated platforms and overhead lattice domes – which were playfully referred to as having a ‘Space Gothic’ design. Combined, these structures created a dramatic yet serene oasis in the middle of the busy fair.
Execution of the US Science Center was only possible because of close collaboration between Yamasaki, Christiansen, and the precast concrete contractors – drawing on a growing local knowledge base in prestress. Tight coordination of mix design, tolerances, and construction schedule were essential to a successful project, and resulted in a remarkably durable Pavilion. Current renovation efforts have largely preserved the original design intent and revealed only few instances of concrete in need of repair or preservation. Operating today as the Pacific Science Center, the Pavilion continues to celebrate scientific achievement and attract young visitors.
In 2014, the Getty Conservation Institute (GCI) organized an experts meeting to assess the concrete conservation field and identify actions that could help practitioners deal with the many technical challenges in conserving this material. This was based on a recognition that reinforced concrete is an integral part of much of 20th century’s built heritage worldwide, and an important contributor to the cultural significance of these sites. The conclusions from this experts meeting have been guiding GCI’s activities to date.
In response, part of GCI’s work has focused on making existing knowledge more accessible to conservation practitioners through publications, and training opportunities. In addition, these dissemination activities aimed to reinforce the connections between the broader concrete field and conservation. That is the guiding premise of the methodology presented in the Conservation Principles for Concrete of Cultural Significance published in 2020.
More recently, the GCI embarked in an international collaboration with Historic England and Laboratoire de Recherche des Monuments Historiques, France, to study the performance of patch repairs executed with the intent to match architectural concrete surfaces. The evaluation of twenty-one sites across the three participating countries was conducted in two phases, starting with documentation and non-destructive assessment of all sites, followed by in-depth investigation of a select number of sites, including sample collection for laboratory analysis. The results of this research reinforce the need for more consistent adoption of a methodology based on sound concrete repair and conservation knowledge, and the need for more craftspeople, engineers, architects, and conservators skilled in concrete conservation. The goal is to use these results to provide practical guidance in the repair of culturally significant concrete, adding to the already existing resources to help guide and train more professionals in the concrete conservation field.
The presentation will cover: Who the International Masonry Institute and International Masonry Training and Education Foundation are and what our function is with the Bricklayers Union. We will talk about our collaboration with International Concrete Repair Institute (ICRI) and the certificate program. We will also talk about our other certificate programs and how they function in specification language in construction projects. We will talk about how and why the concrete repair certificate program was developed and what training we do for the concrete program. We will dive into our infrastructure here in the United States and what will be needed for concrete repair. We will talk about condition assessment concerning concrete and how to better educate our craftworkers not only of the repairs themselves but also for them to gain knowledge to what can cause certain failures and some of the testing that associated with condition assessment. After the diagnostic part of the repair class we get into repair materials, methods and techniques. We will talk about mix design for repairing historic concrete structures. The mix design will cover the use of different types of gravels, sands and Portland cements. We will cover consolidation and compaction of materials along with key application requirements and finishes to match existing concrete structures.
The future of cementitious materials is changing, and this session lays out the vision for the pursuit of greater sustainability for construction by the cement and concrete industry. The Portland Cement Association’s Roadmap to Carbon Neutrality outlines opportunities at all stages of the value chain for cement-based construction.
One way that cement manufacturers are responding to environmental concerns is with an increased range of products and formulations. Blended cements offer an opportunity to reduce the global warming potential (GWP) of cement that in turn reduces the carbon footprint for concrete construction. The ASTM C595 blended cement standard provides four blended cement types to offer greater choices to specifiers and other users. As of mid-2023, more than 50% of cement used in the U.S. was blended cement, largely due to the increased uptake of Type IL portland-limestone cement (PLC) that began in 2021. In 2024, cement manufacturers continue to explore additional blended cement formulations to reduce their environmental impacts. A switch from ASTM C150 portland cement to an ASTM C595 blended cement requires evaluation of fresh and hardened concrete properties to understand appropriate adjustments to mixtures and installation practices when necessary. Based on lessons learned from the experience with PLC, this session describes common issues to consider and potential modifications to practices that will enable successful implementation of any blended cement.