How the ancient Egyptians built the pyramids matters to climate change.

 

Spoiler alert: We may be wrong about how the ancient Egyptians built the Great Pyramids. Decades of schoolchildren are taught the prevailing theory: The pyramids were constructed from enormous blocks of solid stone, cut by hand from far away quarries, and hauled across the searing desert sands. We imagine—thanks in large part to Cecil B. DeMille—thousands of shirtless, sweating slaves harnessed to thick hemp ropes, dragging enormous square blocks of stone up steep ramps. The feat seems so incredible that some wonder whether the Egyptians had help from other planets. Always a rational voice in the room, Neil deGrasse Tyson counters, “Just because you can’t figure out how ancient civilizations built stuff, doesn’t mean they got help from aliens.”

Figuring out how the pyramids were built has interesting applications beyond Egyptology. Today’s building materials do not have an expected lifespan anywhere near 4,000 years. And many of our modern construction processes consume so much energy and emit so much CO2 that we’re quickly destroying the very world we’re working to build. The Egyptians seemed to know something we don’t about using locally sourced materials to construct extraordinarily durable buildings without the huge environmental footprint so common today. Did the Egyptians use their minds as much as their muscle, and if so, what can we learn from them?

The skepticism Tyson addresses comes from a logical place. Despite the common teachings of the building of the pyramids at Giza, the feat of construction seems almost implausible. The Great Pyramid of Khufu was the tallest man-made structure on earth for over 3,800 years—16 times as long as our country has existed—until the construction of the Lincoln Cathedral in England. When built, the pyramid was 756 feet long on each side, 481 feet high, and composed of 2.3 million stones weighing on average nearly three tons each. Many of the joints between the blocks are so accurate that a human hair cannot be passed between adjoining blocks.

According to what we’ve been taught, quarried stone blocks weighing several tons were hauled to the pyramids, before the invention of the wheel. They were quarried out of the hillside with tools made of copper. And a city’s worth of laborers were housed and worked in a cramped area for decades. It’s difficult to imagine and little evidence exists to support this idea—no copper tools have been found around the site, no evidence remains of housing laborers, and no clear hieroglyphs exist documenting the quarrying, transportation, or ramp-lifting of these blocks.

In the 1980s, a French materials scientist named Joseph Davidovits proposed a different theory—the Egyptians didn’t haul the blocks to the pyramids but rather made the blocks one at a time in place on the pyramids. Davidovits suggested that the blocks were formed by pouring an ancient concrete—he called it geopolymer—into wooden molds. A fraction of the laborers would be needed to haul sacks of moist geopolymer concrete to wooden forms placed exactly where each block was needed. Joints between poured concrete blocks would always be perfectly accurate as a compacted moist mixture hardens against neighboring blocks. Davidovits suggested that the geopolymer concrete was made from crushed limestone, clay, water, and lime, a highly alkaline activator that caused the crushed limestone mixture to reconstitute into a man-made stone.

Davidovits’s theory caused quite a stir among Egyptologists, historians, materials science researchers, and anyone who cared that a well-established explanation for the construction of something as iconic as an Egyptian pyramid was being turned on its head. Not only that, but if the Egyptians cast block in place from an early form of concrete, many established theories assigning the invention of mass-produced concrete to the Romans would be off by a few thousand years.

One would imagine that modern scientists with electron microscopes could prove in short order whether Davidovits was correct. Michel Barsoum, professor of materials science at Drexel University and a native of Egypt, never meant to get into the study of the pyramids but was amazed to hear Davidovits’s theory. Barsoum was more amazed to find that no one had proved—or disproved—the idea.

Left: A gash in the side of one of the pyramids shows a combination of irregularly cut quarried limestone blocks surrounded by tight-jointed, cast-in-place geopolymer blocks. Middle: Curved, perfectly aligned joints between these backing blocks are evidence of the blocks being cast in place rather than poured. Right: A ground level block in front of the Great Pyramid of Khufu includes an irregular lip at the bottom. This lip indicates that the block was cast in place. Images © Michel Barsoum, used with permission.

Barsoum, along with a graduate student named Adrish Ganguly, began studying samples from the inner and outer casings of the pyramids. What they thought would be a months-long study turned into a five-year odyssey. In the end, they disproved some of Davidovits’s assumptions but proved his overall theory.

Barsoum believes that the Egyptians did cast a small but significant portion of the block in the pyramids. His electron microscope analysis indicates the Egyptians didn’t use clay in the geopolymer mixture, as Davidovits proposed, but rather diatomaceous earth, a naturally occurring, commonly found soft sedimentary rock formed from the fossilized remains of algae.

And Barsoum importantly disagrees with Davidovits by suggesting that not all the blocks were cast-in-place geopolymer. Rather, Barsoum suggests that the Egyptians used both man-made cast block along with limestone block quarried and hauled to the site in the way our traditional explanation proposes. Barsoum believes that only the exterior casing blocks and the blocks at the higher levels of the pyramids were cast geopolymer blocks. This makes sense: The casing blocks were visible, so cast-in-place block with extremely accurate “joints” would be appropriate to exterior application. And the blocks at higher levels of the pyramids were harder to reach for quarried blocks hauled up ramps—replacing these with cast-in-place geopolymer blocks made the process easier.

Linn Hobbs, professor of materials science at the Massachusetts Institute of Technology, has also added to Davidovits’s original theory and Barsoum’s corroborating research. Hobbs’s students have reverse engineered a geopolymer concrete made from crushed limestone, kaolinite, silica, and natron salts, a substance found in the evaporated remains of saline lake beds. The Egyptians used natron salts for mummification. When exposed to water, natron salts become alkaline, a perfect activator to make a geopolymer reaction.

As predicted, new theories that suggest that even a small portion of the stones in the pyramids at Giza were man-made blocks formed from an early form of concrete have erupted into a firestorm of resistance and vitriol, most notably from those with the most to lose when an established theory is pulled apart. As much as Barsoum assumed that solid materials analysis could indisputably prove how some of the pyramid’s blocks were made, the debate still rages on.

Cement factory in China. The production of cement alone is responsible for 6 percent of the world’s CO2 emissions. Image ©Jonathan Kos-Read, used with permission of Creative Commons license.

Separating the debate from the historical discussion can shed important light on how we can improve today’s construction materials by exploring what the Egyptians might have done. Just the idea of an ancient form of geopolymer concrete masonry that has lasted 4,000 years can forever change the way we build today.

Concrete is the most voluminous material made by all humankind. It’s used all around the world in roads, bridges, dams, and buildings. The key binding ingredient in today’s concrete is Portland cement, which alone is responsible for 6 percent of the world’s CO2 output.

And concrete made with Portland cement isn’t as durable as its environmental footprint might warrant. Concrete bridges are often taken out of service after only 50 years, due in part to harsh conditions like road salt, heavy truck traffic, and freeze-thaw cycles. While the relatively stable environment of the Giza pyramids avoids many of the harsh conditions of today’s urban built environment, the 4,000-year durability of the structure indicates the expanded material lifespan possible with geopolymer concrete. When coupled with a much smaller carbon footprint—geopolymer concretes like those the Egyptians likely pioneered have a tenth the carbon footprint of Portland cement–based concretes—geopolymers offer a compelling alternative.

Watershed Materials has developed the first prototype of a new masonry block machine that applies intense compressive force to allow the interparticle contact necessary for geopolymerization of common earthen materials of relatively low reactivity. Along with the design of a new machine for producing sustainable masonry, Watershed Materials is developing mix designs to create strong durable geopolymer masonry from common clays and earthen aggregates found nearly everywhere across the planet.

While we may have been wrong about how the ancient Egyptians built the pyramids, learning the right answer has implications for modern materials science and provides a new way forward toward developing far more durable and sustainable alternatives.

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It has been 15 years since the U.S. Green Building Council (USGBC) launched the Leadership in Energy and Environmental Design (LEED) green building rating system. That first year, 51 projects participated. Today, LEED is the most widely recognized green building program in the world, guiding the design, construction, operations, and maintenance of over 68,000 projects globally.

With the emergence of LEED, USGBC’s mission of market transformation took the first steps toward realization. Credits for single-attribute building products featuring recycled content, certified wood, or regional sourcing prompted manufacturers to not just divulge such characteristics about their products, but also to make the information easy to find. Today, manufacturers of building products routinely offer lists of green attributes through convenient resources.

As the market for green building products continues to evolve and improve, it is clear that LEED must continue to lead if it is to remain relevant. Enter the rating system’s latest update—version 4—where credits have been revised to ensure that they truly add quality to the utility of a project. In the case of building products, this means going beyond crediting single-attributes and toward an integrative life-cycle-based framework by encouraging manufacturers to disclose information about the materials that comprise their products—enabling practitioners to make better decisions.

For well over a decade, Interface—a global manufacture of commercial carpet tile—has offered customers products with single-attribute “green” characteristics, like recycled content. Yet, Mikhail Davis, director of restorative enterprise at Interface, is quick to point out that it was not until the company adopted a life-cycle approach to sustainability that the true impacts of Interface’s products could be understood. In fact, Interface learned that increasing the recycled content could actually increase the environmental footprint of their products if they did it wrong. “Life-cycle assessment gave us a way to model changes to our products in advance to see if they would move the needle in the right direction, rather than creating unintended new impacts, perhaps at a less visible stage of the product life-cycle.” Interface’s early efforts to put recycled content in their products focused on the backing, the component they make themselves. “But a life-cycle assessment showed us that until we got our nylon suppliers on board, we were not going to be able to seriously shrink our impacts,” explains Davis. In 2011, years of supplier engagement bore fruit in the form of the company’s first 100 percent recycled content nylon yarn products, which have a dramatically lower environmental footprint.

The transformative potential of disclosing the life-cycle environmental impacts of building products is not lost on USGBC. One of the ways LEED v4 encourages life-cycle-based decision-making is by crediting projects for using products with fully disclosed ingredients. The most popular reporting tool through which a product’s life-cycle impacts are conveyed is called an Environmental Product Declaration (or EPD). These are comprehensive, internationally harmonized documents through which manufacturers can provide transparency about their products’ ingredients. Think of EPDs like the nutrition facts label on the side of a box of cereal—only for building products. In the case of LEED v4, eligible EPDs must be third-party reviewed and certified.

EPDs are not new. They have been around in Europe since the 1990s. However, only since USGBC took a bold stand on product transparency with LEED v4 has the EPD marketplace blossomed domestically—a testament to LEED’s ability to shift the market. “EPDs have experienced an explosive level of growth. Five years ago, one would be lucky to find 10 or so EPDs, whereas now there are close to 300 to 400 EPDs, when considering all the North American programs,” states Paul M. Firth, product manager at UL Environment, a division of Underwriters Laboratories (UL).

—Paul M. Firth

LEED v4 uses EPDs as a tool to promote product transparency, but it also encourages project teams to use the information to make better choices about building products and, consequently, optimize the life-cycle environmental impacts of a project. This is easier said than done in a burgeoning EPD marketplace. The reality is that the market has not quite matured to the point that EPD comparison and product optimization is widely practical. There are a few particular obstacles to greater market uptake. Confusion abounds regarding the usefulness of EPDs; they frequently offer incomparable information; and program operators (the entities that oversee EPD development) are not regulated by consistent standards.

In order to overcome these obstacles and accelerate market transformation, USGBC and UL Environment entered into an exclusive partnership just over a year ago. The partnership is focusing on building materials and product transparency.

The leading program operator in North America, UL Environment is uniquely positioned to facilitate USGBC’s work through LEED. “We decided to partner with UL because they have demonstrated they can produce and deliver high quality EPDs,” says Sara Cederberg, technical director at USGBC. With over 120 years of experience with manufacturers in industries ranging from electronics and consumer products, to the automotive industry, UL understands the challenges that companies face.

Prior to LEED v4, the organic nature of market activity related to building product life-cycle assessment allowed manufacturers to engage substantively in the creation of a broad range of tools with varying degrees of oversight. Transformation and innovation was decentralized. The trade-off was significant confusion and a slow rate of market maturity.

Acknowledging the confusion, one of the first things to be addressed by the USGBC/UL Environment partnership will be EPD delivery. “We’re starting with EPDs because that’s an area where the consistency and credibility are currently a bit problematic,” explains Firth.

UL Environment ensures that all of their EPDs conform to international standards. However, they go a step farther by delivering a concise transparency summary, which essentially serves as an EPD executive summary. The summaries are usually just a few pages, making essential data more palatable to practitioners. Interface—the first North American company to deliver an EPD—has worked closely with UL Environment for a number of years and understands that the market success of EPDs will hinge on content delivery. Davis states, “We worked with UL Environment to develop the transparency summary format because we understood that EPDs will not increase product transparency if the important EPD facts like material ingredients or carbon footprint are too difficult to find.”

Through a joint EPD program, USGBC and UL are endeavoring to bring a clarity commensurate with the UL transparency summary to the EPD marketplace at large. The belief is if project teams are presented with a succinct and coherent EPD format, then a multi-attribute framework for building product choices may be leveraged more successfully.

The real value in promoting transparency is exposing the detrimental environmental impacts over the creation, usage, and disposal (or reuse) of a product. LEED v4 encourages teams to go one step farther by using the information about the impacts in order to optimize product selection. EPDs are useful because they present life-cycle performance information through numerous distinct environmental impact categories. The problem is that the categories—such as acidification of land and water sources, formation of tropospheric ozone, and eutrophication—are somewhat esoteric and measured in complex units that vary considerably based on which method is adopted for the life-cycle assessment (LCA). Firth affirms, “Ultimately, the goal is to be able to use these EPDs to compare products—currently they are not quite ready for this.”

EPDs simply report the results of an LCA. To the extent that LCAs for similar products may be scoped differently, one can look to the “rules” defining their respective assessments—termed product category rules (PCRs). “In order to produce high quality EPDs, we must first provide robust product category rules,” Cederberg explains. There are a handful of PCR guidance documents available internationally, but they are open to a wide range of interpretation.

To establish greater consistency, USGBC and UL Environment are exploring a common PCR development framework that addresses the aspects of inherent variability in PCRs to date. “One of the reasons the USGBC/UL partnership was launched is to try to help narrow in on those aspects of LCAs, PCRs, and EPDs that need to be refined to best provide information necessary to make an informed comparison,” states Firth.

All Type III (third-party verified) EPDs require an independent agency, called a program operator, to ensure that EPDs are developed in accordance with international standards.

According to USGBC’s Cederberg, another important piece of developing a quality EPD is ensuring the program operator is experienced and credible. “Just like we look for credentials for commissioning agents or require labs to be accredited for testing low emitting materials, so too would we want to be sure that there is a level set for program operators.” The USGBC/UL Environment partnership is in the early stages of developing such criteria.

The intended outcomes of the USGBC/UL Environment partnership focus on the coherence, consistency, and technical rigor of the EPD development process. This in turn will accelerate the rate of market transformation and improve the overall quality of transparency in the building product market sector.

Considering past successes in shifting the marketplace, it makes sense that LEED could serve as a vehicle for greater market transformation. Firth suggests, “Manufacturers will be able to develop and certify EPDs with LEED-specific criteria in mind, thus providing their products a differentiator in the marketplace.”

Davis attests that rigorous product transparency holds the promise of incentivizing manufacturers to take on the tough challenges that will really improve their products, rather than doing just enough to make a product claim. “For example, we could claim recycled content using recycled mineral fillers in a product, but EPDs show that only when we replace high-footprint plastics like nylon with recycled or biobased substitutes can we really reduce our impacts.”

The promise of the partnership, however, goes far beyond LEED. Armed with consistent declarations and comparable data, a more sophisticated marketplace may be able to aggregate building product data to achieve environmental building declarations. Practitioners may eventually be able to optimize impact categories through building information modeling (BIM). It is even conceivable that building occupants will someday be able to observe real-time impacts on a dashboard, such as the LEED Dynamic Plaque.

The USGBC/UL Environment partnership sends a clear message to the marketplace—the stakes for product transparency have just been raised.

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