DES 40A / SAS 43
3 December 2018
UC Davis Social Sciences and Humanities Building – Materials
The UC Davis Social Sciences and Humanities Building, completed in 1994, has been the subject of its fair share of controversy. Architect Antoine Predock designed the building to reflect the topography of California from above, but at the ground level students and staff alike have complained about it being impossible to navigate. Paths require you to go up and down staircases, through interiors and back out again, and just when you think you’ve figured out where to go, you hit a dead end. This is intentional. Predock intended that since it is the “Social Sciences and Humanities” building, the ‘social’ is increased by always needing to stop and ask someone for directions. This maze-like quality along with the shiny exterior has led to the nickname “Death Star” by students. There are other complaints about the building as well. Issues with heat due to the reflective aluminum panels and inefficient design, inconvenient room numbers, and mischievous students taking advantage of its many hidden areas have been the subject of numerous complaints. It is not all bad, though. The view from the top of the towers is downright gorgeous, and (so long as you’re not trying to get somewhere) it is fun to explore. Certainly, the building is unique and interesting, befitting a high-profile university such as UC Davis. But, as fun as they are, are such high-concept low-efficiency buildings sustainable? What are the costs of building for concept rather than efficiency?
This life cycle will focus on four main materials of the Social Sciences and Humanities Building (from here on referred to as the SSHB for ease): Precast concrete and its steel reinforcement, aluminum, and glass. Steel reinforced, precast concrete makes up the bulk of the building, followed by the aluminum panels that give it its iconic shiny surface. Aluminum is also used for the frames of the glass doors and windows, plus the striking glass catwalk between two towers. The amount of energy that goes into extracting, processing, and transporting these materials calls into question the sustainability of these common building materials.
Concrete is made of a mix of cement, a variety of coarse and fine aggregates, water, and sometimes other additives. There are many different variations of concrete depending on the type and amounts of each ingredient, and it is unclear which specific variation was used in the SSHB, but the overall process is largely the same. Concrete, especially precast concrete, is often made-to-order so that the properties of the concrete suit the use. Precast concrete is unique in that the concrete is poured and set off-site and delivered in pieces.
Cement makes up approximately 12% of most concrete and is used as a binder to hold all the other ingredients together. It contains limestone and gypsum for calcium, clay or sand for silicon, and bauxite or iron to add certain properties. Cement can also contain other additives such as “PFA [pulverized fuel ash], granulated ground blastfurnace slag [a byproduct of steel production] (GGBS), and microsilica (MS)”(Levitt, 5). The properties of the cement will be different depending on which ingredients are used. According to the Environmental Research Group at the University of British Columbia, it takes approximately 3,200-3,500 pounds of raw material to produce 1 ton of cement. On top of that, manufacturing 1 ton of cement produces 1 ton of carbon dioxide. With concrete making up most of 140,000 square feet of the SSH, and one ton of concrete being about 0.49 cubic yards (about 5.6 square feet), that is approximately a bit under 784,000 tons of carbon dioxide produced for just one building – and that’s for the cement alone.
To make concrete, cement is mixed with a variety of aggregates depending on the desired properties. Aggregates make up about 75% of concrete by volume. These aggregates are categorized by density and whether they are natural or synthetic. Normal Weight Aggregates (NWA) include flint from land or marine sources, limestone or sandstone (with limestone more commonly used in architecture), and granite or basalt. Low Density Aggregates (LWA) include sintered PFA, pumice, plastics, and slag. High Density Aggregates (HWA) include barytes, ironstone, and iron. As mentioned previously, it is unknown exactly what mixture was used for the SSH. Limestone is widely used in architecture, though, so it is somewhat safe to assume it was used.
While it is often said that water good enough for drinking is good enough for concrete, this is not always the case, especially with precast concrete. “A concrete block manufacturer is known to use filtered sea water for mixing”(Levitt 14). Fortunately, water used for the processing of certain aggregates (such as washing the salt off of marine-based ones) is often suitable to be used in the concrete itself.
Additives that may be used in concrete production include PFA, GGBS, and MS as mentioned previous. Each of these are byproducts of concrete-related industries. PFA comes from powdered coal and is collected from the chimneys of steam generators. GGBS is a byproduct of steel production, specifically the smelting of ore. MS is a byproduct of silicon and ferrosilicon production.
Ingredients are mixed and placed into molds that are made-to-order. Molds can be made from steel, timber, concrete, plastics, aluminum, or composite. Each has their own advantages and disadvantages and are used depending on the properties of the concrete being cast. Once in the mold, the concrete is allowed to set and harden in a process called hydration. Once the product is done setting and goes through a quality inspection, it is shipped to the location in air-tight containers to prevent degradation starting early.
Steel bars are used to reinforce the concrete and prevent cracking under tension. The specific amount and arrangement of these steel bars (called rebar) once again depends on the specific needs of the client and the rebar is placed within the mold before the concrete is poured. Steel is made from iron ore or iron scrap that is mixed with coking coal then heated in a furnace to create the steel alloy. Once the molten alloy is mixed, the steel is poured into molds and allowed to harden. It is then reheated so that it can continue to be compressed and shaped until the steel bars are the desired dimensions before finally being allowed to cool. Once checked for quality, they are shipped to the concrete plant. “In the early days of reinforced concrete construction, typical steel cross-sectioned areas were 1-2 percent, but it is not uncommon nowadays to observe a considerable excess of this”(Levitt 50). Reinforcing steel rebars take up a significant portion of a piece of precast concrete.
The metallic look of the SSHB that is part of how it got the nickname “Death Star” was created with aluminum panels. Aluminum is the most common metal on Earth, comprising approximately 8% of the Earth’s crust. Despite being so common, aluminum is almost impossible to find in a pure form because it automatically binds with oxygen. Bauxite, a sedimentary rock with a high aluminum content, is mined instead. Explosives are used to reach bauxite deep underground. Once mined, the bauxite is crushed into a powder then sent to a refinery. At the refinery, the bauxite powder is mixed with a caustic fluid that separates aluminum from the other materials in bauxite. The resulting aluminum oxide, called alumina in its powdered form. Alumina is not pure aluminum as it is still bonded with oxygen atoms. While alumina is being smelted, oxygen is removed by injecting a huge amount of electricity – “enough to power a mid-sized city”(How Stuff Works). What is left at the end of this process is pure aluminum which is then shipped to factories and plants all over the world.
The walls of the SSHB are clad with aluminum panels which give it its futuristic aesthetic. It is likely that a specific aluminum alloy was used to ensure the unique surface, but as there are hundreds of different aluminum alloy combinations, it is unknown exactly which was used. That said, aluminum-silicon is one that is commonly used for architecture because of its wide range of potential colors from grey (like in the SSH) to black.
The final major component of the SSHB are the glass windows and glass catwalk. The specifics of what type of glass was used was not able to be obtained, so this assessment will discuss plate glass most commonly used in construction. Plate glass is made from silica sand, soda ash, dolomite, limestone, nepheline cyanite, salt cake, and water. These ingredients are mixed together and melted in a furnace at 1,500 degrees Celsius. The molten glass is then poured onto a metal sheet to get it perfectly flat and even before it is cooled. Once the glass has hardened, it is cut according to the client’s requested dimensions. Double-glazed windows have two plates of glass with gas in-between to provide insulation. These gasses could be argon, krypton, and/or xenon. “Decreasing the thermal losses from a sealed window will improve building performance, reduce consumer fuel bills and place a lesser burden on the environment from atmosphere pollution”(Weir and Muneer 247).
Some of the materials in the Social Sciences and Humanities Building use the same raw materials in their creation. For instance, silicon is used in concrete, steel, and glass while limestone is used in both concrete and glass. This shows how widely used across industries some of these materials are. A great deal of energy goes into the extraction and processing of these materials, and many of these processes produce a great deal of waste. Architects need to consider the processes behind the materials they use when designing over-the-top buildings like the ‘Death Star.’ It isn’t bad to build interesting, controversial buildings, but when so much energy is used to make a building people don’t like, it can seem like a waste.
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6 December, 2018
Wastes and Emissions in the UC Davis Social Sciences and Humanities Building
The UC Davis Social Sciences and Humanities building was constructed in 1994, and while it is aesthetically impressive and solidly built, it can also be used as a microcosm for discussing the sustainability of the construction industry. After sifting through upwards of one hundred individual documents in the Special Collections office at UC Davis’s Peter J. Shields library, my group was able to ascertain the main materials used in the external structure of the SSH building: precast concrete, aluminum, steel, and glass (University of California Davis). Since a majority of the materials used in the construction of the Social Sciences and Humanities building and construction in general are secondary materials and therefore not readily useable, large amounts of waste - both in terms of emissions and solid material - are exuded at the materials acquisition and processing stages. While industrial strength construction materials are necessary to create long-lasting structures, the growing demand is dangerously unsustainable given the current levels of waste and emissions created at each stage of development.
Concrete makes up the largest portion of construction materials used on the Social Sciences and Humanities building and while it has many structural benefits, including strength, manipulability, and resistance to the elements, its production results in many negative environmental impacts. Portland cement, the primary ingredient in industrial concrete, is made from limestone which requires intensive quarrying to extract (How Cement is Made). Limestone is exposed via explosive charges and drilling, both of which result in alkaline dust that either deposits in nearby bodies of water, chokes nearby flora, or if captured, is stored on site. Furthermore, the blasts can expose sinkholes and cause mines to collapse, or effect the water table by removing or contaminating groundwater with sediment and fuel from mining equipment. Groundwater that is pumped out of limestone quarries is highly salinated and degrades surface water quality if released into rivers (Barber).
The production of concrete involves two distinct factors, combustion and calcination, and these energy intensive processes result in approximately 5% of global CO2 emissions. To further break it down, combustion of fuel - primarily coal - to operate rotary kilns produces .75 tons of CO2 per ton of cement. Calcination, the process by which limestone is heated to produce lime, releases an additional .5 tons of CO2 per ton of cement (Alcala). Another form of waste, is washout water. Water used to clean cement mixers and other equipment is known as washout water, and due to the caustic nature and high ph values of concrete, it can greatly increase the toxicity of freshwater sources and soils (Stormwater Best Management Practice).
Aluminum is used in the outer paneling of the SSH building, and despite being a naturally occurring and fairly abundant material, it requires a large amount of processing that is indicative of a secondary material. The most common means of producing aluminum today is through the Bayer Process, in which bauxite ore is mined, refined, and dissolved in sodium hydroxide in order to isolate alumina. The process of separating the alumina from the bauxite ore creates “red mud”, a mixture of silica, iron oxide, titanium oxide and some radioactive elements such as uranium and radium. More troubling, however, are the trace amounts of toxic elements including arsenic and chromium that can be found in the red slurry. For every ton of aluminum, approximately 1.5 tons of this solid waste is produced and due to the elevated toxicity levels, only a slim fraction is repurposed. The majority of red mud in the U.S. ends up in large reservoirs created by dams, or deposited into bodies of water (Tenorm).
Once the alumina is isolated, the smelting process begins, which is responsible for approximately 0.4 billion tons of CO2 each year. Through the electrolysis process, the bond between molten alumina (aluminum oxide) and oxygen is broken; the pure aluminum is extracted while the oxygen pairs with carbon in a release of CO2 (Hydrogen Production: Electrolysis). The electricity required to accomplish the electrolysis process comes from coal and fossil fuels and creates roughly 55% of the 0.4 billion tons of CO2. The next 20% is emitted through the aforementioned electrolysis process and the final 25% is emitted during the combustion of fossil fuels used by machinery to mine, extract, refine, mold, and transport aluminum materials (Agrawal).
Steel acts as the primary support structure for a majority of concrete buildings; unfortunately, it is responsible for up to 7% of global CO2 emissions, making it unsustainable in the long term (Steel’s Contribution to a Low Carbon Future). The principal ingredients of steel are iron and coking coal. Iron blast mining generates a large amount of inert, harmless waste material like soil and overburden - the material that surrounds iron ore - that is stored in large piles around the extraction site. However, toxic metals such as mercury, zinc, arsenic, lead, and cadmium can be inherent to overburden and leach out into the soil or contaminate ecosystems via runoff if not properly disposed of (Chaturvedi). Another source of waste is mine water which, due to mineral contamination, can become highly acidic, and contain dissolved solids with chemical, radioactive, and salianted properties. Most iron mining is done in the “opencast” method which creates large craters in the earth, that are susceptible to acid mine drainage when natural sulfides are exposed to rain water (Chaturvedi).
Emissions and wastes incurred during the refining process are mainly associated with the amount of coal used to make coke. Coal is transformed into coking coal by being heated in the absence of oxygen by fossil fuels. Aside from the common CO2, SO2, and NOx emissions that are characteristic of burning coal and petroleum, this process yields a fair amount of solid wastes in the form of coal dust, tar sludge, and acid sludge (Coke Manufacturing).
When it is time for iron to become steel, it is combined with coking coal, and scrap steel in a blast furnace that creates an estimated 2.8 tons of CO2 per ton of steel. That being said, there is an alternative method that utilizes an electric furnace to melt scrap metal and it is much less emissions intensive and only produces .6 tons of CO2 per ton of steel. Unfortunately, blast furnace steel manufacturing is the dominant method and roughly 66% of global steel is produced in this way (Watson). Regardless, both methods of creating pure steel result in solid wastes. Liquidized impurities removed from steel after the smelting process is known as slag, a complex blend of silicates, manganese, phosphorous, and metal oxides. While a majority of the refined slag is used as aggregate, slag that is not properly refined or otherwise deemed unfit for reuse is sent to landfill (User Guidelines for Waste).
The Social Science and Humanities building utilizes rows upon rows of aluminum-framed windows across its multi storey facade. Window glass used in most modern buildings is known as “float glass” and is comprised of silica, soda, lime, dolomite, and aluminum oxide, the majority of which can be found in sand and limestone (Glass Manufacturing Industry). The effects of limestone mining has already been discussed, but sand mining has similarly negative impacts on natural ecosystems. Most notable is the depletion of coastal land. For example, according to coastal engineer Ed Thornton, a heavily mined beach near Monterey California is shrinking at a rate of nearly eight acres, per year (Beiser). Subsequently, there is is rapid decrease in fertile soil, groundwater, and water table height, that all culminates in decreased biodiversity. While some aspects of instream mining, suspended particulates for example, are naturally resolved rather quickly, total remediation takes decades (Mishra).
Emissions are almost entirely exclusive to the production phase of glass development. The minerals are smelted in a furnace at temperatures as high as 1500 degrees celsius and the natural gas and liquid fuel used to power the furnaces outgas carbon dioxide. The vaporization of molten glass components creates a significant amount of sodium dioxide and nitrogen oxides (Our Environmental Impact), which when released into the atmosphere and combined with water vapor and sunlight create acid rain and smog respectively (Michelle). Depending on the properties required for specific glass types, additives that release volatile particulates such as lead and arsenic into the atmosphere may be included (Glass Manufacturing).
Recycling and Waste Management
Despite the aforementioned wastes, it should be noted that concrete, aluminum, steel, and glass structures require minimal maintenance once completed and moderate quantities of their waste materials can be recycled into further construction projects. However, the cycle of repurposing construction materials only creates further emissions and eventual wastes and therefore, the issue of sustainability is still very prevalent. Concrete, for example, can be reused in small doses, but in order to maintain structuctural integrity, recycled concrete must be paired with an estimated 5-10% increase of cement. As expected, an increase in cement usage coincides with an increase in carbon dioxide emissions and wastes (Alcalá). Further emissions can be expected from the crushing and separation of concrete materials as well. Window glass is historically difficult to recycle due to the variety of tints, treatments, and frame types, all of which must be separated. The amount of labor associated with isolating glass makes it substantially more expensive to recycle than dispose of, and it is generally relegated to landfill (Lennon).
Aluminum and steel on the other hand are already heavily recycled. Up to 93% of structural steel can be recycled without losing its integrity, making it the most sustainable material in the building by a huge margin (Recycling and Reuse). Aluminum can also be recycled at varying rates, and reuse of construction aluminum creates significantly less emissions than primary aluminum production - though it does not mitigate them completely. That being said, demagging, a process by which secondary aluminum is treated to remove magnesium and other impurities, outgasses vapors from chemicals used in the process such as chlorine gas, aluminum fluoride, and aluminum chloride. Reactions between the aforementioned chemicals and coatings in the scrap metal can create environmental pollutants known as dioxins (Cora). Given the average lifespan of 75-100 years for concrete buildings, time will tell if construction materials from the Social Sciences and Humanities building are effectively recycled and if the waste and emissions are properly managed.
Waste in the construction industry is unavoidable. However, acknowledging the amount of waste produced at each stage is only the first step in creating a more sustainable future. The main issue that has arisen in discussion of more sustainable construction is the lack of cheap material alternatives. Furthermore, recycling construction materials currently poses a myriad of logistical issues. Unfortunately, it seems that technological advancements must first be made before recycling can become an effective means of controlling waste production. That being said, research is being conducted today in an attempt to discover new recycling methods that will hopefully be the key to waste mitigation.
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