Designing with Concrete in the 21st Century  

Concrete is a rather ubiquitous, tested, proven, and versatile building material. It has been used for literally thousands of years to create long-lasting man-made structures of all types, including buildings. Architects in the past few centuries have found it to be an appealing choice to express dynamic and vibrant designs in ways that other materials could not. The ability to structurally reinforce concrete and form it into custom, free-flowing shapes can give it an organic quality that is different from most other materials. This can produce more design freedom and the ability to incorporate unique and custom features into a building as part of the basic construction process. It is not surprising then that new technologies, techniques, and design approaches have been developed that allow architects to think and design with concrete in ways that are even more creative, structurally efficient, sustainable, and cost effective. It is also common to couple the technical knowledge of concrete with the ability to design in three dimensions using building information modeling or similar design software to create award-winning and stunning facilities. Some architects even attest that their careers have not only been made possible but have flourished through this combination.

© Agence Rudy Ricciotti

Architectural concrete is a versatile building material that can provide structure, enclosure, and finish with exceptional design flexibility.

Concrete as a Building Material

Concrete has long been regarded as a remarkable material that is extremely plastic and malleable when newly mixed but exceptionally strong and durable when cured and hardened. These properties come from the fact that it is a man-made combination of some very common natural ingredients that give it these characteristics.

• Gravel or crushed stone: This is the coarse aggregate that makes up the majority of concrete and is fundamentally the source of its strength. Aggregate can vary in type and size and, for practical reasons, is usually sourced locally for a particular project where it is being used.
• Sand: This is the fine aggregate that serves the purpose of filling in the spaces between the coarse aggregate. The ratio of fine to course aggregate can vary depending on the specific concrete mix and the intended final use or appearance of the concrete.
• Cement: While some in the public mistakenly use the term cement when they mean concrete, design professionals are quite aware that cement is just one ingredient of concrete. This is the paste that coats the aggregate with the ability to bond or hold it all together and is typically on the order of only 10 to 15 percent of a concrete mix. While made from natural materials, cement, specifically often portland cement, is a manufactured product that may be shipped in from elsewhere. It is a controlled chemical combination of calcium, silicon, aluminum, iron, and other ingredients. Common raw materials used to obtain those chemicals include limestone, shells, and chalk or marble combined with shale, clay, slate, blast furnace slag, silica sand, and iron ore. These ingredients, when heated at high temperatures, form a rock-like substance that is ground into the fine powder that we know as cement. Different combinations of ingredients can yield different bonding strengths as well as different colors of cement.
• Water: The above materials are all dry and by themselves will not interact to form concrete until an appropriate amount of clean, potable water is added. The hydrogen and oxygen in the water create a chemical reaction called hydration with the chemicals in the cement that allows it to transform and bond all of the aggregates together. As a significant and important chemical ingredient, water may account for 15 to 20 percent of the concrete mix.
• Air: As with any mixing process, some air is inherent in the process of creating concrete. The amount of air can affect the physical properties of the concrete and can be controlled somewhat but will commonly be on the order of 5 to 8 percent of the mix.

Understandably, varying the type and proportions of ingredients will determine different basic characteristics of the concrete, including its overall strength, appearance, color, texture, and the corresponding suitability for different applications. In recent decades, chemical admixtures have been developed that can be added to further influence the final characteristics of concrete.

The Evolution of Concrete

Putting all of these ingredients together didn’t just happen by accident so it is amazing to realize how long people have been using concrete as a building material and how it has been adapted and developed over time.

Early Uses of Concrete

The earliest known use of rudimentary concrete dates back to about 6500 BC in the Middle East (current day southern Syria and northern Jordan) by Nabataea Bedouins who controlled oases in this desert area. They were interested in creating places to store water and found they could mix lime with some local deposits of silica sand and pozzolan (sandy volcanic ash) to create a rather waterproof enclosure. They used a very dry mix of materials with only a little water and would tamp it into place by hand to make it more gel like, producing greater bonding.

Around 3000 BC, ancient Egyptians began to use lime mortars that were similar to concrete in the building of the pyramids. These mortars held the stone and bricks of the pyramids and other structures together but were also placed first as a bedding material for cut stone and bricks. This concrete-like bedding allowed some of the stones to be carved and set with extremely thin joints no wider than ¹/₅₀ of an inch. Around the same time, the Great Wall of China used a form of cement and mortar in and around stone and brickwork. Modern day spectrometer testing has shown that a key ingredient in this mix was glutinous sticky rice among other things.

Concrete in Roman Times

By 600 BC, the Greeks had discovered a natural pozzolan that formed cement when mixed with lime and water and used it somewhat selectively for buildings. The Romans by contrast were very prolific with concrete, although they often used a drier, less plastic version than the Greeks. Initially, this mixture was used more as a means to hold large stones and bricks together. For larger and grander structures, the Romans began to incorporate volcanic sand to react chemically with lime and water, causing hydration and allowing it to cure beautifully under water. This likely represented the first large-scale use of a truly cementitious binding agent as part of concrete and was a part of utilitarian structures like aqueducts, bridges, etc. It was also used for significant buildings, many of which are still standing today, such as some Roman baths, the Pantheon in Rome, and the Colosseum. There was also some experimentation with admixtures, such as animal fat, milk, and blood, to adjust the physical properties of the concrete mixtures. When natural pozzolan aggregate was not readily available, the Romans seem to have learned how to manufacture two types of artificial pozzolans, which reflected a fairly high level of sophistication for the time.

Concrete Advances in the 19^th Century

Like many other things around the time of the Industrial Revolution, the process of producing cement and concrete took many leaps forward in the 1800s. As early as 1793, John Smeaton discovered a modern method for producing hydraulic lime for cement by using limestone containing clay that was fired in a kiln. The resulting stone-like products called “clinker” were then ground into a fine cement powder. This produced a steady and consistent supply of cement that could be shipped to construction locations and mixed with other local ingredients to form concrete for special or unique structures. In 1824, an Englishman named Joseph Aspdin took this process a step further by burning finely ground chalk and clay in a kiln until the carbon dioxide was removed. The resulting product was named “portland” cement because it resembled the light-colored, high-quality building stones found in Portland, England.

Photo courtesy of Pennsylvania and Historical Museum Commission

Portland cement was first developed in England and became popular in the United States in the late 1800s with advances in its production.

It soon became apparent that some engineering was needed to ascertain the true structural properties of different cement and concrete products. Between 1835 and 1850, systematic tests to determine the compressive and tensile strength of cement were first performed, along with the first accurate chemical analyses. By 1860, portland cements of modern composition were produced and manufactured to detailed standards important to the hydration process and the chemical characteristics of the cement. These standards were based on heating a mixture of limestone and clay in a kiln to temperatures between 1,300 degrees Fahrenheit and 1,500 degrees Fahrenheit. In 1885 came the development of a horizontal, slightly tilted kiln that could rotate the cement ingredients and function more efficiently. This rotary kiln provided better temperature control and did a better job of mixing materials so much so that by 1890, rotary kilns dominated the market.

The other significant advance during this time was the evolution of steel products. It didn’t take long to realize that combining concrete with steel reinforcing bars would allow the best of both worlds: the compressive strength of concrete and the tensile strength of steel. By the late 1870s, the first steel-reinforced concrete buildings came into existence and have been a common structural system ever since. However, despite all of these advances, concrete during this time was still seen as a utilitarian material to be used for mostly industrial and infrastructure projects.

Concrete in the 20^th Century

By the early 1900s, the variations in concrete types and capabilities called out a need for standards. Founded in 1904 and headquartered in Farmington Hills, Michigan, the American Concrete Institute (ACI) quickly became the leading authority and resource for the development and distribution of not only consensus-based standards but also technical resources, educational and training programs, and, more recently, certification programs. Membership was, and still is, open to individuals and organizations involved in concrete design, construction, and materials who share a commitment to pursuing the best use of concrete. (ACI has since grown to over 95 chapters, 110 student chapters, and nearly 20,000 members spanning more than 120 countries.) Soon after, in 1916, The Portland Cement Association (PCA) was founded as a policy, research, education, and market intelligence organization serving America’s cement manufacturers. The stated purpose of the PCA is to promote safety, sustainability, and innovation in all aspects of construction, foster continuous improvement in cement manufacturing and distribution, and generally promote economic growth and sound infrastructure investment. (Today, PCA members represent 92 percent of U.S. cement production capacity and have facilities in all 50 states.)

As ACI and PCA resources became better known and the industrialization focus of the 1800s passed to the more vision-focused modern movement in the 1900s, reinforced concrete started to become a material of choice by well-known architects who used it for many notable buildings. Not only did it provide the ability to create a fire-proof structure, but air-entraining agents and other chemical admixtures that were developed in the 1930s increased resistance to freezing and improved workability. These attributes solved a number of technical issues, but the plastic, malleable qualities of poured-in-place concrete offered exciting new design possibilities, too. Architects could begin to investigate concrete forms that could either be cubist and rectilinear or free flowing and expressive of nature. Increasing expertise with reinforced concrete allowed thin shell construction, which employed thinner concrete slabs and shapes than previously. New forms, such as parabolic arches and hyperbolic paraboloid roof structures, began to be used. The Sydney Opera House in Sydney, Australia, became a mid-century poster child for the artistic use of concrete formed into segments of spheres to produce a dramatic structure that appeared light and airy, like sails on a ship. Other structures like Saarinen’s Washington Dulles International Airport and TWA Flight Center at John F. Kennedy International Airport became equally iconic in the United States.

During this time, high-rise building construction using concrete also became common. In dense urban areas, buildings were getting taller and construction techniques were needed that could provide both an efficient structure and fire proofing. Reinforced concrete fit the bill in many cases, allowing vertical columns and other supports to be tied directly into the horizontal floor and roof slabs that they supported. Even steel-framed buildings tended to rely on the use of either precast or cast-in-place concrete for floors. Construction companies became known for how efficiently and how well they could “get concrete up in the air.”

Twenty-First Century Capabilities

Today, we are the beneficiaries of all of the past exploration, technical development, and creative experimentation by associations, design professionals, and construction companies that have worked with concrete. Further refinements into materials research, engineering, and the science of concrete combined with new design methods and technology have allowed architects to demonstrate innovative and exciting new capabilities. We will look at a few of those recent developments here.

High-Strength Concrete

The PCA points out that the key to achieving a strong, durable concrete rests in the careful proportioning and mixing of the ingredients. A mixture that does not have enough cement paste to fill all the voids between the aggregates will be difficult to place, produce rough surfaces, and will be porous. A mixture with an excess of cement paste will be easy to place and will produce a smooth surface; however, the resulting concrete is not usually cost effective and can more easily crack.

Concrete is commonly defined structurally in terms of its compressive strength. Because it is custom mixed and subject to human variation, it is routine to require test cylinders to be pulled from each mix or batch that is used in a building. In order to obtain a determination of actual strength, measured cylinders can be filled and allowed to cure up to 28 days. At that point, the cylinders are removed from around the concrete and hydraulic testing equipment can be used to determine how much pressure the concrete can withstand before breaking or otherwise failing.

The combination of engineering and years of test results have allowed those who specialize in concrete mixing and production techniques to gain a good understanding of how to formulate the mixtures to accurately predict the strength of cured concrete and design accordingly. The common, medium-strength concrete used in a lot of building construction is usually specified to withstand about 4,000 pounds per square inch (psi) of pressure. Some installations where strength is less important can be approximately of 2,000 to 3,000 psi, while concrete that needs to be more durable and may be thinner (such as sidewalks) is usually on the order of 5,000 to 6,000 psi.

© Agence Rudy Ricciotti

At the Musée Jean Cocteau – Collection Severin Wunderman in Menton, France, (2007), concrete is used to establish a rectilinear enclosure with a curved and flowing design expression.

In recent times, the question has been raised about whether or not concrete of even higher strengths than these are possible. During the past two decades, researchers and engineers have worked with the chemistry of cement and concrete to answer that question with a resounding yes by developing mixes that yield higher strengths than previously typical. Although there is no precise point of separation between high-strength concrete and normal-strength concrete, ACI has defined any concrete with a compressive strength above 6,000 psi to be termed high-strength concrete. Those engaged in the development of high-strength concrete were influenced by experts from the early 1970s who predicted that the practical compressive strength limit of ready-mixed concrete would unlikely be able to exceed 11,000 psi. However, modern development and testing have achieved compressive strengths of up to 12,000+ psi with two buildings in Seattle, containing concrete with a compressive strength of an incredible 19,000 psi.

The manufacture of high-strength concrete involves making optimal use of the basic ingredients that constitute normal-strength concrete. Those who produce it have learned the specific factors that affect compressive strength and how to manipulate those factors to achieve greater strength. In addition to selecting a high-quality portland cement, they optimize aggregates, then optimize the combination of materials by varying the proportions of cement, water, aggregates, and admixtures. For example, when selecting aggregates for high-strength concrete, the inherent strength and optimum size of different aggregates are considered. In looking at the bond between the cement paste and the aggregates, the surface characteristics of the aggregate as well as the characteristics of the cement are considered. Any of these properties could enhance or limit the final capabilities of high-strength concrete.

Taking things up to an even higher level, ultra-high-performance concrete (UHPC), also known as reactive powder concrete (RPC), has been developed as a high-strength, ductile material. The material provides compressive strengths up to an astounding 29,000 psi but also provides flexural strengths up to 7,000 psi. The flexural or ductile behavior of this material is a new first for concrete—concrete has not previously had the ready capacity to deform and support flexural and tensile loads. Normally, rock and concrete respond to structural stress either by breaking or bending. When rock or concrete breaks, it is called brittle deformation since any material that breaks into pieces exhibits brittle behavior. When rock or concrete actually bends or flows, it is called ductile deformation, meaning the material deforms but stays intact. We normally think of metals, such as steel, deforming in this way so the ability of UHPC to do this is unique to concrete construction. It is formulated by combining portland cement, silica fume, quartz flour, fine silica sand, a high-range water reducer, water, and steel or organic fibers. Using this material for construction becomes simplified since reinforcing steel may be able to be eliminated. It may, in some cases, be dry cast or self-placed with minimal use of formwork. UHPC also exhibits superior durability characteristics due to a combination of fine powders selected for their grain size (maximum 600 micrometer) and chemical reactivity. The net effect is a maximum compactness and a small, disconnected pore structure.

What does this mean for building design? High-strength and ultra-high-performance concrete provide new possibilities for high-rise buildings and other structures where greater strength and thinner profiles (i.e., less weight) are important. This newly available combination of superior properties and design flexibility can facilitate the architect’s ability to create attractive flat, curved, or multidimensional shapes. It can also offer solutions with advantages like speed of construction, improved aesthetics, superior durability, and impermeability against corrosion, abrasion, and impact, which can mean reduced maintenance and a longer life span for the structure.

Architectural and Decorative Concrete

The term “architectural concrete” refers to concrete that, while providing a structural function, also achieves an aesthetic finish to a building. By contrast, “decorative concrete” typically refers to concrete flatwork or building elements that are enhanced with texture or color but are not structural building components. In either case, the concrete can be mixed and treated to take almost any form, texture, or color. Forming is a matter of creating the appropriate forms or molds for the material to be set into.

© Agence Rudy Ricciotti

Concrete can be formulated by adjusting the type and proportion of ingredients to achieve a range of compressive and even tensile loading strengths.

Texture here refers to the finished surfaces, which can be very smooth, patterned, or intentionally rough. A sometimes popular decorative surface technique uses exposed aggregate, which is achieved by removing the outer layer of cement and exposing the inner aggregate particles. This might be performed using chemical surface retarders, sandblasting, water blasting, acid etching, or other techniques. Nonetheless, it becomes important to select the aggregates that will be exposed based on the characteristics needed to achieve good results— i.e., color, hardness, size, shape, durability, and cost. Some popular decorative aggregates include things like quartz, granite, marble, limestone, and gravel or manufactured materials such as alkali-resistant glass and ceramics.

Photo courtesy Gerner, Kronick + Valcarcel, Architects

Architectural concrete can be fashioned into a broad range of appearances and finishes in addition to providing structural support to a facade or overall building.

The colors of architectural or decorative concrete can vary based on the aggregates in the mix to create a wide range of integral hues. Color can also be affected by the cement used since each has different inherent color tones as a result of slight differences in raw material ingredients and manufacturing processes. Portland cement can retain its white color if it is made of select materials that contain negligible amounts of iron and manganese oxides, which can otherwise give cement a gray color. Architectural or decorative concrete can also be enhanced by adding mineral oxide pigments to add some specific coloring. When lighter shades of color are desired, white cement should be used, but reds, tans, and dark gray hues can be produced using gray cement.

Textures and patterns in the surface of architectural and decorative concrete are quite possible using forms and form liners. Artistic, free-form, or geometric patterns can be produced this way, or the surface can simulate other materials, such as brick, stone, and wood. Form liners are readily available made from aluminum with stock brick-pattern faces or with vertical rib or board-and-batten patterns. Custom variations are possible, too. The benefits of taking this approach include an enhanced visual appearance to a wall or facade, and the ability to camouflage any subtle differences in texture and color found on the surface of the concrete. Overall, the result allows for the creation of a well-designed surface that is complete unto itself whether it provides structural support or not.

Light-Transmitting Concrete

Concrete has the properties of being quite solid, heavy, and dense so it’s not surprising that it is thought of in those terms. However, some recent developments have given designers a chance to think quite differently about concrete as a material that can bring light into a space in creative and surprising ways. Some researchers and companies have begun embedding optical fibers that run from one side of a section of concrete to the other, quite effectively transmitting light from one side to the other. Depending on the materials and conditions of this experimental approach, colors and light have been found to remain remarkably consistent throughout the concrete. In some cases, the optical fibers have been able to carry light over 50 feet without significantly impacting the other properties of the concrete since they occupy only a small percentage of the total concrete block or panel.

Architects and others have begun to imagine many artistic and functional applications for this innovative concrete development. Daylighting is a real possibility with the ability to carry and direct light exactly where needed for uniform, glare-free installations. Optical fibers are known to transmit light so effectively that there is virtually no loss of light conducted through the fibers so the effectiveness of this approach has great potential. It is also possible to transmit natural or artificial light to areas that need it because of a lack of other light. For example, experimentation is being done to light indoor fire escapes in case of a power failure or to illuminate sidewalks at night.

Fabricating light-transmitting concrete has been done in a variety of ways. In some cases, fiber filaments were placed individually in the concrete, which was, not surprisingly, quite time consuming and costly. Semi-automatic production processes have also been tried using woven fiber fabric instead of single filaments. In this case, the fabric and concrete are alternately inserted into molds at predetermined intervals. In order to protect the fibers from damage, the concrete mixture is made from fine materials only, without any coarse aggregate. Once the concrete is added into a form with the pre-placed fibers, it can be cut into panels or blocks for use in buildings. The surface can be left unfinished or be polished, resulting in a semi-gloss or even a high-gloss finish.

© Agence Rudy Ricciotti

Concrete in the 21^st century can be formulated and formed to provide characteristics not previously available, such as the ability to be self-cleaning or the ability to transmit light through optical fibers.

Self-cleaning Concrete

One of the problems of any exterior building surface, particularly high-rise buildings, is how to keep the exterior clean over time. Any porous stone, masonry, or concrete often suffers from a collection of dirt, dust, and pollution over time that darkens the color of the building and reveals the fact that it is indeed quite dirty. Beyond the aesthetic disappointment of such a condition, the pollutants and dirt, particularly when wet, could react with and begin to degrade the building materials. In order to address this problem, some recently introduced formulations of cement have been found to be capable of neutralizing pollution, turning otherwise harmful smog into compounds that are quite harmless and can be washed away. Since these cement formulations are comparable to using portland cements, they are ideal for exposed concrete buildings.

The technology that makes this possible is based on adding particles of titanium dioxide to white or gray cement, during its manufacture. Doing so does not change the fundamental character of the cement allowing it to work like any other portland cement for use in all varieties of concrete. The added chemical simply works together with sunlight to break down smog or other pollution that have become attached to the concrete. The process is known as photocatalysis and relies on sunlight hitting the surface of the concrete to neutralize most organic and some inorganic pollutants, thus avoiding discoloration. Of particular interest to building owners, the titanium dioxide acts simply as a catalyst that does not disappear as it breaks down pollution, and continues to keep working over time. Typically, this photocatalytic concrete creates a reaction with common hydrocarbon pollutants and produces less harmful chemical byproducts, such as oxygen, water, and small amounts of carbon dioxide. Wind or rainwater can then readily wash these materials away from the concrete surface, allowing buildings to stay cleaner without the need for added chemical or mechanical cleaning. This has been shown to be true even in highly polluted locations, such as the white concrete Air France headquarters building at Roissy-Charles de Gaulle International Airport near Paris, which remains white due to the self-cleaning concrete used.

An additional potential benefit to using a titanium dioxide formulation in concrete is the ability to help cleanse the air. Fossil fuel combustion in cars and buildings emits invisible air pollution including carbon dioxide (CO₂), nitrogen oxide (NO_x), and sulfur oxide (SO_x) that can lead to acid rain, smog, global warming, and respiratory issues. Photocatalytic concrete exposed to sunlight has been shown to foster the natural breakdown of harmful NO_x into harmless nitrates. Without the catalyst, the NO_x breaks down in the atmosphere that we all breathe. How well might this work? A study conducted in the Netherlands used photocatalytic concrete pavers on a section of a busy roadway and monitored the air quality between 19.5 to 58.5 inches above the pavement. This was done in both a control area with normal pavers and the test section with photocatalytic pavers. The results found that the NO_x levels were reduced by 25 to 45 percent by using the photocatalytic concrete.

More Sustainable Concrete

While concrete is made primarily from natural materials, the process of creating it requires significant effort and energy, which impacts its determination of sustainability. The best method used to determine the degree of sustainability of any material is to conduct a life-cycle assessment that addresses extraction of raw materials, transporting them, processing them (particularly with energy), incorporating them into buildings, and finally recovering them at the end of the service life of the building for either recycling, reuse, or disposal. National and international standards have been developed for conducting such a life-cycle assessment that begin with product category rules (PCRs) for a particular type of material or product. ASTM International has produced just such a document for assessing cement known as UN CPC 3744, “Portland, Blended Hydraulic, Masonry, Mortar, and Plastic (Stucco) Cements.” This document can be used by cement manufacturers to produce environmental product declarations (EPDs) that identify the specific environmental impacts of their products. Those impacts are presented in terms of environmental, energy, and material/waste effects from using the product. By requesting EPDs from different cement manufacturers and comparing the results, architects and others can determine the differences in the short- and long-term environmental impacts of those products.

Source: ASTM International

ASTM International has produced UN CPC 3744, “Portland, Blended Hydraulic, Masonry, Mortar, and Plastic (Stucco) Cements.” This document can be used by cement manufacturers to produce environmental product declarations (EPDs) that identify the specific environmental impacts of their products.

Many who have looked at portland cement, concrete, and sustainability have determined that the long-term benefits of the material can be shown to outweigh initial impacts of producing it, thus producing a more favorable life-cycle assessment. In 2009, the Concrete Sustainability Hub (CSHub) was established as a research center at the Massachusetts Institute of Technology (MIT) in collaboration with the PCA to address the sustainability and environmental implications of the production and use of concrete. Its research aims to fine tune the composition of concrete, reduce the greenhouse gas emissions of its production, and quantify its environmental impact and cost during the entire life span of an infrastructure or building project.

Among the findings of CSHub and others, concrete can contribute to green and sustainable building designs in several ways.

• Permeable concrete allows rainwater to percolate into the soil more naturally, helping to promote better drainage for more sustainable sites.
• Thermal mass can be provided in buildings using concrete that, when designed appropriately, can improve overall energy performance.
• Recycled materials can be incorporated into concrete mixes as substitutes for stone aggregates in order to avoid new material extractions. The use of fly ash or slag in particular in concrete mixes has been seen as a positive way to harvest and neutralize some otherwise problematic products of coal combustion.
• Local manufacturing of concrete and cement helps to reduce the energy used in transporting heavy materials.
• Durability as a material means that concrete has a long-lasting service life compared to many other building materials. It’s inherent strength and resistance to weather allow very resilient structures to be constructed out of concrete.

Based on these attributes and a full life-cycle assessment, architects, engineers, cement manufacturers, concrete mix companies, and construction operations can all address green and sustainable attributes of buildings by selecting the most appropriate cement and concrete formulations for their projects.

Using Building Information Modeling for Concrete Design and Construction

The advances in the science and technology of concrete in buildings has been notable and impressive over the past 100 years or so. But even more rapid and significant changes have taken place in the design and construction processes as computerized design and documentation have become the norm around the world. Specifically, the availability of design software that works in three dimensions and allows design professionals to literally model a building out of stock or custom components and materials has helped to completely redefine the way buildings are being designed.

A computerized building information model (BIM) uses specific 3-D components to design, shape, and assemble a virtual building. Each of the components have definable attributes that match the size, shape, and specifications of the systems, materials, or products that they represent. In practice, the implication is that the task is no longer one of drafting but of creating, assessing, revising, and recreating in three dimensions as needed. This can allow a great deal of design experimentation to be done rapidly, as different aspects of the design can be explored in great detail and over multiple iterations. When it comes to using concrete, it means that forms, shapes, geometries, and other attributes can be modeled using the power of the computer to do the math and provide real data on the differences between designs.

Beyond experimenting with forms of concrete through BIM, computer analysis can be used to determine the structural performance of concrete designs. In this case, the geometric parameters can be linked with the identified structural loads imposed on the concrete to determine the needed physical properties of the concrete for compressive and flexural strength. Coordination of the BIM software with structural engineering software may be the most appropriate way for a design team to work on such projects and allow full collaboration on optimizing the design not only visually but structurally as well. In that way, the best thickness and quantity of concrete can be determined to perform as intended without over-designing, thus controlling costs.

BIM also allows for computerized visualization of the connectivity of concrete with other materials used in the building construction. These may be other structural elements, such as steel, masonry, or wood members, that attach or are embedded in the concrete, or it may be openings such as windows and doors. It can also be used to coordinate proper insulation and air-sealing techniques when architectural concrete is used as part of the building enclosure that effects energy performance. If the focus is on decorative concrete or aesthetic issues, then BIM is ideal at presenting three-dimensional visualizations in great detail in order for designers to assess and determine the best choices.

Overall, the use of computerized building information models makes the process of designing innovative concrete buildings quite effective. The nature of a shared BIM allows collaborative opportunities between all disciplines and even community members. The high-quality visualizations coupled with the technical and structural coordination to create precise and accurate models empower truly collaborative decision making because all participants can share an articulated understanding of the relevant design issues and together determine the most appropriate solutions.

Conclusion

Concrete has long been, and continues to be, a significant building material that provides a full range of structural, architectural, and sustainability options. The science and technology of concrete has advanced notably to allow for a range of uses and capabilities that have been proven in countless buildings as well as industrial and infrastructure projects. Combining these capabilities with advances in computerized building information modeling allows entire design teams to work together to achieve designs that are truly representative of 21^st century thinking and possibilities. Further, the longevity of concrete means that these constructed designs will likely endure for generations to come.

CASE STUDY: EXPRESSING THE ESSENCE OF STRUCTURE

Photos courtesy Gerner, Kronick + Valcarcel, Architects (www.gkvarchitects.com)

Project: The Beekman – Restoration and Adaptive Reuse
Architects: Gerner, Kronick + Valcarcel, Architects (GKV)
Location: 5 Beekman Street, New York City
Size: 340,000 square feet

The Project: The Beekman is actually a multi-building project. The project includes the restoration and adaptive reuse project of an historic 10-story landmark office building, known as Temple Court, into a boutique hotel, as well as construction of a 51-story, 68-unit condominium addition on an adjacent lot. The first 10 floors of the new building, aligning with Temple Court, are joined to the hotel, and the upper floors are designed as residential condominiums. Built in 1883, the Temple Court Building was the first “fireproof” building in New York and is an early example of the use of brick and terra cotta for an office building. The restored building and the new building combine the best of historic character with modern amenities and design values.

Design Approach: The firm is known for reviving the notion of expressing the essence of structure, particularly through the use of cast-in-place concrete. It draws inspiration from well-known architects of the mid 1900s, including I.M. Pei, Paul Rudolph, and Le Corbusier, who used exposed cast-in-place concrete to create many great buildings. As other construction technologies became available, however, cast-in-place concrete became comparatively more expensive and even cost prohibitive in some cases. GKV has innovated new design and construction techniques based on roadway construction that could be adapted to architecture. This allows it to design buildings, like The Beekman, that have more character, are greener, more cost effective, safer, and most importantly to the architects, to create a brand new aesthetic. The firm is known for using carefully designed exposed concrete frames created by using custom concrete form liners, often with artistically inspired patterns to create decorative facades.

Three-Dimensional Design: These innovative solutions are accomplished through the use of three-dimensional, computerized design software that has become the norm for everyone in the 60-person firm to use as their work platform. Firm Founding Principal Randolph Gerner, AIA, says, “I don’t think my career would be where it is today without 3-D design software.” He notes that it allows him to easily and readily visualize details or entire buildings in three dimensions. And the software that it employs is not intimidating at all—he boasts that he can create designs with it “all by myself” before passing them on to others in the firm to work on.

CASE STUDY: HARMONIZING EARTH AND ARCHITECTURE

Photos courtesy of Norihiko Dan and Associates

Project: The Sun Moon Lake Administration Office of the Tourism Bureau
Architect: Norihiko Dan and Associates
Location: Sun Moon Lake, Yuchi Township, Taiwan
Size: 6,639 square meters (71,462 square feet)

The Project: Sun Moon Lake is the largest body of water in the country of Taiwan (Republic of China) as well as a popular tourist attraction. When the Tourism Bureau of Taiwan sought to locate its administrative offices there, it used the “Landform Series” of the New Taiwan by Design International Competition as a basis to select a design firm. Japanese architect Norihiko Dan and Associates received first prize in the competition and went on to design the facility. A well-known architect and urban designer, Norihiko Dan is also a passionate environmental activist. Born in 1956 in Kanagawa Prefecture, Japan, Dan studied architecture at Tokyo University and won the Graduation Design Prize in 1979. For his postgraduate work at the same university, he studied under the notable Fumihiko Maki. Dan then went on to complete his master’s degree at the Yale School of Architecture in 1984. He founded his own firm, Norihiko Dan and Associates, in Tokyo in 1986. Presently, the firm employs about 15 people, and it concentrates on public and private architecture and interior design, as well as landscape design, civil engineering, urban design, and art and furniture design.

The Design Approach: Dan’s visions are guided by what’s best for the planet, and this is evident in his design of this project as well as many others done by the firm. “My favorite part about this particular project is that it is half architecture and half landform, which creates a beautiful and uninterrupted whole,” explains Dan. The firm spent a lot of time considering the actual site. “The design approach for modern architecture lies in breaking down the architectural mass into parts, or to compose them, to create the building,” he begins. In the interest of working with nature, it considered ways that the need for excavating thousands of cubic meters of earth could be turned into a benefit for the site and the overall design. Then inspiration struck. “If we compare this project to curry, the cubic meters of dirt would be the ‘sauce’ and the cubic meters of architecture would be the ‘rice, meat, and vegetables.’ So we would actually make a larger amount of curry in total. I decided to use this idea as my starting point.” He reasoned that if it did not actually remove the dirt from the site, but rather used it again within the same site, it could avoid damaging the environment, even on this small scale. If the “curry” mix were comprised of half-architecture, half-landscape ingredients, the team could create a green hill to balance and recover the surface area that the building had eaten up. If it started with the “sauce,” it could modify their design to fit any site formation, just as curry or stew can fit in any pot, no matter what form. “I named this curry-like architecture and land mixture a ‘universal form’ to lead this conceptual solution to a more solidified state.”

Joyful Design: The design team needed to build the bridge between internal and external logic, meaning ‘internal’ functional requirements, and the ‘external’ influencers like the surrounding area or even the mountains framing the site from a distance.” In the Sun Moon Lake Administration Office Building project, great care was taken to bridge these internal and external logics. The result was a seamless mix of earth and architecture. Part of the structure is built into the hillside with a green roof cover that helps to regulate internal temperatures. Dan and his team use three-dimensional building information model software to create all of their designs from conception to completion. They commonly make use of powerful 3-D modeling tool sets, specifically using NURBS curves to draw an incredible number of freeform shapes and surfaces. They found that the ease of use and efficiency offered by the programs design-focused tools helps increase their productivity dramatically. Further, the ability to visualize in three dimensions and create dramatic renderings likely contributed to their selection as the competition winner.

Norihiko Dan has created many other notable works that have garnered praise from the New Taiwan by Design International Competition, such as the Floating Tea House, which also received first prize honors in recent years in the competition’s “Landform Series.” The redevelopment of the Taiwan Taoyuan International Airport Terminal 1 won first prize in the “Gateway Series” category of the competition. His philosophy is simple. “We try to work earnestly and joyfully on every field of architecture design,” he says. “We’re inspired by every formative natural art—by their very existence and especially their interesting and complicated histories.” Dan continues to produce work according to his Universal Form Theory, garnering great recognition—and bettering the world around him—along the way.

Peter J. Arsenault, FAIA, NCARB, LEED AP, is a practicing architect, green building consultant, continuing education presenter, and prolific author engaged nationwide in advancing building performance through better design. www.linkedin.com/in/pjaarch

Vectorworks, Inc. is the developer of Vectorworks software, a line of industry-specific CAD and BIM solutions that help more than half a million design visionaries transform the world. www.vectorworks.net