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Solving the concrete paradox: How rebuilding Turkey could pave the way to a more sustainable future

By using a common form of clay as a supplement in the production of cement, manufacturers might reduce their carbon emissions by as much as 75 percent.

Solving the concrete paradox: How rebuilding Turkey could pave the way to a more sustainable future
[Source photo: Hakan Akgun/dia images/Getty Images]

In the early morning hours of February 6, 2023, Turkey experienced its most powerful earthquake in more than 80 years.  The quake, 7.8 on the Richter scale, together with strong aftershocks, killed more than 50,000 people, left one and a half million people homeless, and destroyed more than 210,000 buildings. It created enough rubble to cover about 40 square miles (twice the size of Manhattan) a yard deep in debris.  A UN estimate puts the damage to Turkey’s built environment at more than $100 billion.  More than a hundred countries, the UN, the World Bank, and other global and local charities are stepping up with billions of dollars worth of assistance and loans.

The Turkish government has pledged to build 319,000 new houses in the next year, promising greater oversight to prevent corrupt construction practices that resulted in substandard concrete buildings and contributed to the magnitude of the recent destruction.

But Turkey’s urgent mission to respond to a tragic disaster also illustrates the global bind we find ourselves in at this particular moment in our evolution on our planet: The very same material we rely on to both protect us from environmental hazards and to rebuild after them—concrete—is the world’s second biggest source of carbon emissions, fueling a climate crisis that is generating more extreme weather, leading to more disasters and destruction.  Call it the concrete paradox.

Whether you lean towards optimism or skepticism regarding an Erdogan-led government’s promises to root out corruption, this much is true: As Turkey rebuilds, it can rely on the same basic kind of carbon-emitting portland cement-based concrete used for the buildings that were wrecked, or it can find a way to utilize more sustainable concrete that dials back carbon emissions.


Many people conflate concrete and cement, but cement is an ingredient in concrete. It’s what binds the other components—sand, gravel, water—together. Sand, gravel and water have minimal carbon footprints. The most popular kind of cement—portland cement—has a big one. It’s the world’s second biggest source of carbon emissions.

The world’s largest cement companies no longer even attempt to dodge the problem.  Their annual reports, websites, executive speeches, and richly funded R&D programs all emphasize the aim to reach carbon neutrality. Four years ago, trade association meetings hardly touched sustainability; now they’re dominated by the topic. The cement and concrete industries are surprisingly, even hearteningly, blunt about the dangers of its carbon footprint and the need to drastically reduce CO2 emissions. There is no shortage of viable low-carbon alternatives to ordinary portland cement, but nearly every solution is at least a decade away from widespread use.

But there is one viable short-term solution that could dramatically reduce CO2 emissions: supplementing conventional limestone clinker with calcined kaolin clay.

Portland cement derives from limestone that must be baked in giant kilns to 2700 F. Carbon emitting fossil fuels are the only practical option for heating the kilns to such extreme temperatures. In addition, limestone (the Earth’s largest store of carbon) loses its carbon content when it is kilned. A modern cement plant can drive out carbon from thousands of tons of limestone a day; each year, the industry produces the equivalent of 1,200 pounds of cement for every single person on the planet—along with 1,000 pounds of carbon emissions per person on earth.

Following kilning, remaining carbon-free limestone ends up as small pellets known as clinker. The clinker pellets are then ground down to make up the bulk of portland cement. The ratio of clinker in cement is called its clinker factor. The level of clinker factor is the key to cement’s emissions. Cutting the clinker factor in cement by substituting clinker with less-carbon-emitting materials is the key to driving down cement’s carbon footprint.

Which is where kaolin clay comes in.  It’s a common clay found all over the world.  Some types of kaolin clays are used to make porcelain, but there are a wide variety of types that can be used for other industrial purposes. One purpose is to supplement and replace a large portion of clinker. Heating kaolin clay to around 1300 F calcines it—this makes it reactive enough so that when it combines with some clinker the structural properties of the final cement are undiminished.

Turkey has an abundant supply of kaolin clay, says Kemal Celik, professor of civil and structural engineering at NYU Abu Dhabi. Limestone calcined clay cement, also called LC3, is a material with a much lower clinker factor, and thus far lower carbon emissions, than mainstream cement.

Currently, calcined clay, when combined with ground limestone, can reduce cement’s emission by around 40 percent. Research out of a group led by Karen Scrivener at Switzerland’s EPFL technical university suggests this can eventually be pushed as high as 75 percent. A materials engineer from England, Scrivener is one of the world’s top experts on cementitious materials. She is LC3’s most prominent researcher and chief evangelist driven by the conviction that the material is the world’s only choice to reduce emissions from concrete by the 50 percent dictated by the Paris Agreement’s 2030 climate goals. She travels the world in an effort to get the world to act quickly on its adoption and carries with her a world map that shows all the places in nearly every part of the globe where the necessary raw materials are abundant. Turkey is flush with it.

“LC3 is the only cement available at scale for decarbonizing the industry in time to meet the targets,” Scrivener recently told me at an industry gathering in San Francisco, “but it will take producing millions of tons of LC3 before the end of the decade.”

As a product for the world market, LC3 is not yet ready to replace all traditional portland cement. Some of the cement giants, including Holcim in France and Argos in Colombia, have already devoted plants to making it. The world’s largest LC3 plant is being built in Ghana near Accra by a consortium of African and Scandinavian investors. Scrivener was on hand for the announcement to build the plant. Making LC3 doesn’t require a wholly new cement plant. Older, even obsolete cement plants can be repurposed to process the clays. That’s been done in Japan.

Celik says that cement made with calcined clay already meets the Turkish standards, and while the country doesn’t yet have a facility for making it, Turkey does not need to develop its calcined clay industry from scratch. It’s already one the world’s largest producers and exporters (after the U .S., India, and China) of kaolin clays for other processes such as the manufacture of ceramics, paints, and plastics, though not nearly at a scale that would transform the cement and concrete industries.


The most significant obstacle in Turkey, Celik says, is economic. “Supplementary materials are mostly not used,” he says, “because the materials don’t sacrifice any strength compared to the standard materials but they also reduce the cost of cement.”

In other words, the less carbon-emitting cement option costs less and is therefore less profitable.

“Is there is there a rationale [in Turkey] for doing things differently going forward? Absolutely,” says Pedro Martins Barata, a V.P. at the Environmental Defense Fund. Barata oversees the EDF’s efforts to develop carbon markets to address climate challenges. “Nobody wants the earthquake and nobody wishes it. But [rebuilding sustainably] is the thin silver lining on a catastrophic event. So to that extent, since you have that opportunity, let’s grab that, let’s have those minimum requirements, and let’s replan and plan on a different, low carbon [approach]. That’s where the role of development agencies, the national planning agencies, etc, comes in.”

Setting sustainable priorities and lining up incentives in the earliest stages of a construction project are the most important steps to bake in carbon reductions as it proceeds. The Turkish government and its international partners have the clout to both entice and demand sustainable rebuilding. The African Development Bank has pioneered a model for sustainable building: it’s adaptation benefits mechanism (ABM).  Though they have several moving parts, ABMs basically pay the builders extra money for the every unit of a resilient or sustainable project they put up.  The payments are based on savings yielded over time as compared to the costs of less resilient approaches. Another approach, suggested by Firat Yucesoy, the engineer founder of Gemina International, one of Turkey’s largest materials trading companies, is to offer favorable credit terms to cement manufacturers and contractors who commit to sustainable cement and concrete, an approach he says that would be especially attractive at a time of tight credit and high interest rates. Turkey, Yucesoy notes, is the world’s largest exporter of cement and other building supplies, and trends in its materials sector have an outsized influence on materials worldwide.

Celik sees the use of calcined clays as part of more comprehensive strategies to lower carbon emissions over the long-run in the rebuilt zones. He recommends erecting resilient building designs to last a hundred years or more, smart city planning that makes room for gardens and forested spaces, and the integrating renewable energy to the region which today relies largely on coal-fired power plants.


When the world was cobbling together the United Nations following the devastation of WWII, Winston Churchill reputedly opined “Never let a good crisis go to waste.” Few discrete current building projects in the world will reach the scale of the post-earthquake reconstruction in Turkey. Nearly any big change in the cement industry takes years to implement and the effects unfold over decades.

“There is only one investment cycle between now and 2050 for the industry to rethink how to produce low-carbon cement and concrete to drive down the emissions from business as usual,” says Radhika Lalit, principal of the Cement and Concrete Initiative at the Rocky Mountain Institute. “What we build today will be around in 2050 and we’re memorializing the carbon inside these buildings primarily through concrete, which cannot be undone.”

If sustainable concrete can be deployed in Turkey, the rebuilding can literally and figuratively pave the way for the rest of the world. The world is expected to double, and perhaps triple the built environment by 2060. Much of that building will be driven by population growth, the rise of the global middle class and by urbanization. But there will also be a lot of concrete spent to build resilience to disasters and in rebuilding after disasters strike. Sea rise alone is estimated to put hundreds of millions of coastal residents at risk and require more than $1 trillion worth of sea walls. Building those walls with standard portland cement would be like bailing out a boat and learning that every bucket of water removed causes two more buckets’ worth to flood in.

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A former trader and member of the Chicago Mercantile Exchange, Ted C. Fishman is the author of China, Inc. and Shock of Gray. His writing has appeared in The New York Times Magazine, Harper’s, Esquire, and many other publications. He is working on a book about concrete for W.W. Norton. More